Expert tips to maximize your email success.
A best practice guide for email deliverability.
JUMP TO SECTION
Email deliverability roadblocks
Strategy and key metrics for deliverability
Why email deliverability matters
Metrics that matter for email deliverability
Creating positive first impressions
Content best practices for optimal email deliverability
Keep volume and strategy consistent
Explore how to improve your email deliverability.
In this digital era, people expect to be wowed quickly — and competition is fierce. Between computers, cell phones, smart home equipment, and supported channels such as instant messaging, email, web, push, and social media, consumers are bombarded with content. If a message isn’t compelling, they’re likely to delete it or entirely disengage with your brand.
To stand out, you’ll need to give your customers unique, personalized, and extremely relevant experiences. That requires an integrated, dynamic multichannel strategy that keeps your audience engaged. An email marketing program is central to that strategy — but an email can only make an impact if it reaches the recipient’s inbox.
This guide will help you understand key email deliverability terms, concepts, and strategies, so that you stay ahead of the curve. It includes a strategy to keep your email channel at the forefront of your marketing mix by prioritizing deliverability, inbox placement, and revenue.
Email deliverability roadblocks.
Email deliverability, a critical component of every sender’s marketing program success, is characterized by ever-changing criteria and rules. Internet service providers (ISPs) have a continual need to prevent spammers, so they develop sophisticated filtering techniques to protect customers. Email senders can become unintentionally ensnared in those efforts. Effectively navigating this digital world to best reach your audiences requires regular tuning of your email strategy, with consideration of key deliverability trends.
According to Forbes, email users are expected to grow to 4.73 billion globally by the end of 2026. Gone are the days of sending maximum volumes of email for minimal conversion. The reality is that considering volume alone puts your highly engaged customers at risk of not receiving their emails. This can have major revenue implications for you as a sender. Viewing email as a low-cost channel with unlimited potential is challenging and fragile.
Strategy and key metrics for deliverability.
Delivery rate
This is the percentage of emails that do not bounce and are accepted by the ISP.
Inbox placement
For emails accepted by the ISP, this metric determines whether the email lands in the recipient’s inbox or spam folder.
In other words, a high delivery rate is not the only facet of deliverability. Understanding both the delivered rate and the inbox placement rate is a must for accurately measuring email performance. Just because a message is received via an ISP’s initial checkpoint doesn’t necessarily mean that your subscriber saw your message and interacted with it.
Designing successful email marketing campaigns depends on having a clear understanding of marketing goals, whether they’re for prospecting or nurturing customer relationship initiatives. This helps determine who to target, what to promote, and when outreach is ideal. Email marketing strategy objectives may include:
Converting prospects into first-time buyers
Enhancing customer satisfaction and brand loyalty
Growing customer relationships with new offerings
Reactivating lost or lapsed customers
Why email deliverability matters.
If you don’t know whether your emails are getting delivered or landing in the inbox versus the spam folder, you should.
Countless hours go into the planning and production of your email campaigns. If emails bounce or land in your subscribers’ spam folder, your customers probably won’t read them, your call to action (CTA) won’t be acknowledged, and you’ll fall short of your revenue goals due to lost conversions. Put simply, you can’t afford to ignore deliverability. It’s crucial to the success of your email marketing efforts and your bottom line.
Following deliverability best practices gives your email the best possible chance of opens, clicks, and the ultimate goal — conversions. You can write a brilliant subject line, add beautiful imagery, and craft engaging content. However, if the email doesn’t get delivered, the customer has no opportunity to convert. All in all, in email deliverability, each step in the acceptance process is dependent on the previous one for program success.
Key factors for successful email delivery.
To ensure your emails reach their intended recipients effectively, consider the following key factors:
Solid infrastructure
Implement proper IP and domain configuration, feedback loop (FBL) setup (including complaint monitoring and processing), and regular bounce processing. Adobe handles this setup on behalf of our clients.
Strong authentication
Apply Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC) to verify email authenticity.
High list quality
Maintain explicit opt-in, use valid email acquisition methods, and follow engagement policies to build high-quality email lists.
Consistent sending cadence
Keep a steady email sending schedule and minimize volume fluctuations.
High IP and domain reputation
Uphold a strong sender reputation to avoid being marked as spam.
Key factors for email inbox placement.
ISPs use unique, complex, and ever-changing algorithms to determine whether your email lands in the inbox or spam folder. Focus on these important factors to improve inbox placement:
- Delivered email rate
- High engagement
- Low complaint rate (under 0.1%)
- Consistent sending volume
- Minimal spam traps
- Low hard bounce rate
- No blocklist issues
Key factors for email engagement clicks.
To maximize ROI from your email campaigns and improve click rates, your emails must reach your audience and drive engagement. Here are some important factors to consider:
- Delivered and opened emails
- Compelling, clear CTAs
- Relevant, valuable content
Key factors to improve email engagement open rate.
To maximize your email open rates, consider these crucial factors:
- Inbox placement
- Brand recognition
- Compelling subject line and preheaders
- Personalization
- Optimal frequency
- Content relevance
Key factors for conversion.
To optimize your conversion rates, consider these critical factors that influence the entire customer journey:
- Incorporate key drivers of click rate, such as email delivery, strong CTA, and relevant content.
- Transition from email via a clickable link to a landing page or sales page.
- Design a user-friendly, visually appealing landing page with a clear path to conversion.
- Maintain brand recognition, perception, and loyalty.
Potential impact on revenue.
The following chart illustrates the potential loss in revenue that a weak deliverability policy can have on your marketing program. As shown, for a business with a 2% conversion rate and an average purchase of $100, every 10% reduction in inbox placement equals almost $20,000 in lost revenue. These numbers are unique for every sender.
Metrics that matter for email deliverability.
Bounces.
Bounces are one of the primary factors that ISPs use to determine IP reputation. A bounce occurs when an email delivery attempt fails and the ISP sends a failure notice back to the sender. Proper bounce handling is critical for list hygiene. After a given email has bounced several times in a row, this process flags it for suppression, so the system doesn’t continue sending to invalid email addresses. The number and type of bounces required to trigger suppression varies by system.
“Delivered” versus “bounced” is the most common way of measuring the delivery of marketing messages: The higher the delivered percentage, the better. There are two types of bounces: hard bounce and soft bounce.
Hard bounces.
Hard bounces are permanent failures that occur after an ISP determines a mailing attempt to a subscriber’s address is unsuccessful. These addressed are categorized as undeliverable and added to the quarantine, which means they won’t be reattempted. There are some cases in which a hard bounce is ignored if the cause of the failure is unknown.
Here are some common examples of hard bounces:
- Address doesn’t exist
- Account disabled
- Bad syntax
- Invalid domain
Soft bounces.
Soft bounces are temporary failures that an ISP generates when it has difficulty delivering an email. These are retried several times to achieve a successful delivery (depending on whether custom or out-of-the-box delivery settings are used). Addresses that continually soft-bounce will not be added to quarantine until the maximum number of retries has been reached (which also varies depending on settings).
Some common causes of soft bounces include:
- Mailbox full
- Receiving email server down
- Sender reputation issues
- User unknown
- Unreachable (5.5x)
- Account disabled
- Refused (Spam complaint)
- Invalid domain
- Unreachable (4.4x)
- Mailbox full
- Account disabled
- Refused
- Out of office
- Technical error
Complaints.
Complaints are registered when a recipient indicates an email is unwanted or unexpected. This action is typically logged through the subscriber’s email client when they hit the spam button or via a third-party spam reporting system.
ISP complaint.
Most tier 1 and some tier 2 ISPs provide a spam reporting method to users because opt-out and unsubscribe processes have been used maliciously in the past to validate email addresses. The Adobe platform will receive these complaints via ISP feedback loops. This is established during the setup process for any ISPs that provide feedback loops (FBLs) and allows the Adobe platform to automatically add email addresses that have been reported to the quarantine table for suppression. Spikes in ISP complaints can be an indicator of poor list quality, less-than-optimal list collection methods, or weak engagement policies. They’re also often noted when content is not relevant.
Third-party complaints.
Several anti-spam groups allow spam reporting at a broader level. Complaint metrics used by third parties tag email content to identify spam, a process commonly referred to as fingerprinting. Users of these methods are generally more knowledgeable about emails, so they can have a greater impact than other complaints if left unanswered.
Spam traps.
Spam traps are addresses that ISPs use to identify unsolicited emails from fraudulent senders or those that aren’t following email best practices. Spam trap addresses are not published and are almost impossible to identify. Delivering email to spam traps can impact your reputation with varying degrees of severity, depending on the type of trap and the ISP. Let’s explore the different types of spam traps.
Recycled.
Recycled spam traps are addresses that were once valid but are no longer being used. One way to keep lists as clean as possible is to regularly send an email to your entire list and accurately suppress bounced emails. This ensures abandoned email addresses are quarantined and withheld from further use.
In some cases, an address can become recycled within 30 days. Sending regularly is a vital aspect of good list hygiene, along with regularly suppressing inactive users.
Blocklisting.
Blocklisting occurs when a third-party blocklist manager registers spam-like behavior associated with a sender. The cause of a blocklist is sometimes published by the blocklisting party. A listing is generally based on IP address, but in more severe cases, it can apply to an IP range or even a sending domain. Resolving blocklisting should involve support from your Adobe deliverability consultant to fully eliminate the issue and prevent further listings. Some listings are extremely severe and can cause long-lasting reputation issues that are difficult to resolve. The result of a blocklist varies by provider but can impact the delivery of all emails.
Bulking.
Bulking refers to emails being delivered to the spam or junk folder by an ISP. It’s identified when a lower-than-normal open rate (and sometimes click rate) occurs alongside a high delivery rate. Bulking happens for different reasons based on the ISP. In general, if messages are placed in the bulk folder, it signals a reputation issue — like list hygiene — that requires reevaluation. This problem needs to be corrected immediately before it affects future campaigns. Work with your Adobe deliverability consultant to remedy any bulking issues.
Pristine.
A pristine spam trap is an address that has never belonged to an end user and exists solely to identify spam emails. This is the most impactful type of spam trap, as it’s virtually impossible to identify and would require a substantial effort to clean from your list. Most blocklists use pristine spam traps to list unreliable senders. The only way to avoid these traps from infecting your broader marketing email list is with a double opt-in process for list collection.
Blocking.
A block occurs when spam indicators reach proprietary ISP thresholds, causing the ISP to block email from a sender (noticeable through bounced mailing attempts). There are various types of blocks. Generally, blocks apply to an IP address, but they can also occur at the sending domain or entity level. Resolving a block requires specific expertise, so please contact your Adobe deliverability consultant for assistance.
Typo.
A typo spam trap is an address that contains a misspelling or malformation. This often occurs with known misspellings of major domains like Gmail (Gmail is a common typo). ISPs and other blocklist operators will register such known bad domains to be used as a spam trap to identify spammers and measure sender health. The best way to prevent typo spam traps is to use a double opt-in process for list collection.
Email engagement.
One of your biggest areas of focus should be engagement. Let’s first cover why it’s so important, and then how to improve it.
Engagement has become the most important factor impacting inbox placement decisions. Over the years, ISPs have shifted focus from content-related filters to a behavioral model, heavily relying on positive and negative engagement actions. Positive engagement primarily includes opens, clicks, forwards, and replies. Negative engagement includes deleting without opening, ignoring, unsubscribing, and marking as spam. Receiving explicit permission is the foundation of positive email engagement. Once a brand has permission, that relationship should be nurtured by regularly measuring and meeting the customers’ expectations through frequency and content.
A good open and click rate varies. Check with your deliverability consultant to establish specific goals and baselines for your email program.
Email engagement is also used to describe a type of metric that helps determine IP reputation. ISPs that own portals (Hotmail, AOL, Yahoo, Gmail, etc.) on the B2C side, as well as email hosting and filter providers on the B2B side, have a tremendous amount of data regarding customers’ interactions with emails. These entities can see opens, clicks, and many other forms of interaction — even if email is moved in or out of the spam folder. They can also see if the email address it was sent to is in the client’s address book or not.
While you, as a sender, cannot track all engagement metrics, opens and clicks are a good starting point. It’s important to note that ISPs only have visibility into email engagement. Also, with the rollout of Apple’s mail privacy protection initiative in September 2021, it has become even more important for senders to monitor all types of engagement signals from their subscribers. This includes website visits, social media interactions, purchasing activity, and behavior.
Emphasize quality over quantity.
From a deliverability standpoint, it’s important to build a quality list of highly engaged subscribers. Continuously sending emails to an unresponsive audience can negatively impact your sending reputation and increase the likelihood of your email landing in the spam or junk folders.
Mailing frequency is equally important when creating and maintaining an email marketing program. Setting the recipients’ expectations during your welcome message is a very useful strategy — people like to know what to expect. Yet those expectations need to be met. Sending emails too often can cause customer fatigue and may lead to increased complaints and unsubscribes.
Each marketer must find the right frequency for their specific marketing program. We suggest testing different frequencies to find the right balance.
Interests are always changing.
Subscriber interests are constantly evolving, and marketers need to understand that commitment to a brand may be temporary. Some subscribers will opt out, but many will just delete or ignore unwanted emails. From a consumer’s perspective, any message that is unsolicited or unwanted is perceived as spam. Therefore, marketers need to rely on permission-based marketing and monitor engagement for loss of interest. In order to achieve optimal inbox placement, we recommend that marketers strategically reengage subscribers using reactivation campaigns and a “win-back strategy.”
A win-back strategy involves sending special incentives to a targeted segment of a marketing database to reengage subscribers with low open and click rates. Positive responses are kept, and the portion of the list that doesn’t respond is moved to an inactive status list that no longer receives emails.
A reactivation campaign is similar but is used to reconfirm a list. This is useful when dealing with old, stale lists that haven’t been emailed for over 12 months. This type of campaign is typically enforced by blocklists to resolve a block. The subscribers who are not successfully reengaged should be excluded from future email promotions.
Your win-back or reactivation campaign will be unique to your email program and should be fully customized for your business needs.
Reply-to is engagement too.
It’s easy to just set your reply-to email to a “no-reply” address, but this would be a mistake that overlooks the bigger picture.
When recipients reply to marketing emails, a response is expected. By enabling a reply-and-response system, you help boost your sender reputation. This will increase the likelihood of positive deliverability and inbox placement rates. It’s also a much better customer experience and will enhance consumer perception of your brand. After all, nothing says “please do business with us” like “we want to hear from you.”
If you do have a real email address they can reply to, make sure someone is monitoring it and that it’s not just an auto-response. If it’s not monitored, the missed expectations can frustrate customers and lead to complaints or lower engagement.
Switching email platforms.
Infrastructure.
Email infrastructure is a core element of successful deliverability. A properly built email infrastructure includes multiple components — specifically domains and IP addresses. These components are the machinery behind the emails you send, and they’re often the foundation of your sending reputation. Deliverability consultants ensure that these elements are set up properly during implementation, but because of their impact on reputation, it’s important for you to have a basic understanding of how it all works.
Domain setup and strategy.
Times have changed, and some ISPs (like Gmail and Yahoo) now use sending reputation as an additional reputation indicator. Your domain reputation is based on your sending domain instead of your IP address. This means that your domain takes precedence when it comes to ISP filtering decisions. Part of the onboarding process for new senders on Adobe platforms includes setting up your sending domains and properly establishing your infrastructure. You should work with an expert on the domains you plan to use in the long term.
Here are some tips for a good domain strategy:
- Choose a domain that clearly reflects your brand, so users don’t mistake emails for spam.
- Avoid using your parent or corporate domain, as it could impact email delivery from your organization to ISPs.
- Consider using a subdomain of your parent domain to legitimize your sending domain.
- Use separate subdomains for transactional and marketing messages. Transactional emails are triggered by user actions and typically provide valuable information to customers. Keeping them distinct ensures that transactional traffic does not affect the reputation of your marketing subdomain.
- Use a branded envelope-from domain as it is important for B2B marketers. Many hosting and filter providers evaluate the reputation of the envelope-from domain when determining sender reputation.
IP strategy.
It’s important to form a well-structured IP strategy to help establish a positive reputation. The number of IPs and setups varies depending on your business model and marketing goals. Work with an expert to develop a clear strategy.
Consider the following as you build the IP/domain strategy for your brand:
- Using a large number of IP addresses to spread out the spam load, or “snowshoe,” is common among spammers. Even though you’re not a spammer, you might look like one if you use too many IPs, especially if those IPs haven’t had any prior traffic.
- Too few IPs can cause slow email throughput and potentially trigger reputation issues. Throughput varies by ISP — how much and how quickly an ISP is willing to accept email is typically based on its infrastructure and sending reputation thresholds.
- It may also be advisable to separate different products or marketing streams into distinct IP pools if your reputation varies drastically across them. Some marketers also segment by region. Separating the IP for lower-reputation traffic won’t fix the issue, but it will help protect your ‘good’ email deliveries. After all, you don’t want to sacrifice your good audience for a riskier one.
Feedback loops (FBLs).
Behind the scenes, Adobe platforms are processing bounces, complaints, unsubscribes, and more. Setting up these FBLs is an important aspect of deliverability. Complaints can damage your reputation, so you should suppress email addresses that register complaints from your target audience. Gmail, however, doesn’t provide this data, which makes list-unsubscribe headers and engagement filtering especially important for Gmail audiences, who now make up the majority of subscriber databases.
Authentication.
ISPs use authentication to validate the identity of a sender. The two most common authentication protocols are Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM). These are not visible to the end user but do help ISPs filter email from verified senders. Domain-based Message Authentication, Reporting, and Conformance (DMARC) is gaining popularity and is currently supported by all major email providers (such as Google, Microsoft, Yahoo, etc.).
SPF
An authentication method that allows the owner of a domain to specify which email servers they use to send email.
DKIM
An authentication method that is used to detect forged sender addresses (commonly called spoofing). When DKIM is enabled, the receiver can confirm that the message originated from your organization.
DMARC
An authentication method that allows owners to protect their domains from unauthorized use. DMARC uses SPF, DKIM, or both to control what happens to email that fails authentication: whether it is delivered, quarantined, or rejected.
Targeting criteria.
When sending new traffic, target only your highly engaged users during the early phases of IP warming — the process of gradually increasing email volume from a new IP address. This helps establish a positive reputation from the start and effectively builds trust before introducing your less engaged audiences. Here’s a basic formula for engagement:
ISP-specific considerations during IP warming.
ISPs have different rules and ways of looking at traffic. For example, Gmail is one of the most sophisticated ISPs because it looks at engagement very strictly (opens and clicks) in addition to all other reputation measures. This requires a customized plan that only targets the highly engaged users at the onset. Other ISPs may require a customized plan as well. Work with your Adobe deliverability consultant on these ISP-specific strategies.
Volume.
The volume of email you are sending is critical to establishing a positive reputation. Put yourself in an ISP’s shoes — if you start seeing a ton of traffic from someone you don’t know, you’d be alarmed. Sending a large volume of email right away is risky and sure to cause reputation issues that are often difficult to resolve. It can be frustrating, time-consuming, and costly to dig yourself out of a poor reputation and the bulking and blocking issues that result from sending too much too soon.
Volume thresholds vary by ISP and can also depend on your average engagement metrics. Some senders require a very low and slow ramp in volume, whereas others may allow for a steeper ramp. We recommend working with an expert, such as an Adobe deliverability consultant, to develop a customized volume plan.
Here’s a list of tips for a smooth transition:
- Permission is the foundation of any successful email program.
- Start with low sending volumes and then increase as you establish your sender reputation.
- A tandem mailing strategy allows you to ramp up volume on your Adobe solution while winding down with your current ESP, without disrupting your email calendar.
- Engagement matters, so start with the subscribers who open and click your emails regularly.
- Follow the plan — our recommendations have helped hundreds of Adobe clients successfully ramp up their email programs.
- Monitor your reply email account. It’s a bad experience for your customers if you use noreply@xyz.com or do not respond to their replies.
- Inactive addresses can have a negative impact on deliverability. Reactivate and repermission addresses on your current platform before switching to new IPs.
- Use a sending domain that’s a subdomain of your company. For example, if your company's domain is xyz.com, email.xyz.com provides more credibility to the ISPs than xyzemail.com.
- Registration details for your email domain should be available publicly and not kept private.
Purchase confirmations
high engagement
Cart abandonment
medium-high engagement
Welcome emails
high engagement, but can contain bad addresses depending on your list collection methods
Win-back emails
lower engagement
Creating positive first impressions.
Address collection and list growth.
The best sources of new email addresses are direct channels, such as sign-ups on your website or in physical stores. In these cases, you can control the experience to ensure it is positive and that the subscriber genuinely wants to receive emails from your brand.
In-person collection of email addresses, such as in-store, trade shows, and industry events lists, can present challenges as verbal or handwritten inputs are prone to spelling errors and typos. You can mitigate such challenges by sending a confirmation email as soon as possible after sign-up.
The most common type of website sign-up is single opt-in, which should be the absolute minimum standard for acquiring email addresses. It’s when the owner of an email address grants permission to receive marketing emails, usually by submitting the address via a web form or in-store sign-up. While it’s possible to run a successful email campaign using this method, it can lead to certain challenges.
- Unconfirmed email addresses can have typos or be malformed, incorrect, or maliciously used. Typos and malformed addresses cause high bounce rates, which can and do provoke blocks issued by ISPs or IP reputation loss.
- Malicious submission of known spam traps (sometimes called “list poisoning”) can cause problems with delivery and reputation if the trap owner takes action. It’s impossible to know if the recipient truly wants to be added to a marketing list without confirmation. This also makes it difficult to set expectations and can lead to increased spam complaints — and sometimes blocklisting if the collected email address happens to be a spam trap.
Subscribers often use throwaway addresses, expired addresses, or addresses that do not belong to them to get what they want from a website while avoiding being added to marketing lists. When this happens, marketers’ lists can result in a high number of hard bounces, increased spam complaint rates, and subscribers who do not click, open, or positively engage with emails. This can be viewed as a red flag by mailbox providers and ISPs.
Sign-up forms.
Beyond gathering essential data about your new subscribers — which helps foster more meaningful connections with your customers — there are a few additional steps you should take to optimize your website’s sign-up form.
- Clearly communicate with your subscribers by confirming their consent to receive emails, outlining what content they can expect, and specifying how often they will hear from you.
- Add options allowing the subscriber to select the frequency or type of communications they receive. This way, you’ll know the subscriber’s preferences from the start and can provide the best possible experience.
- Balance the risk of losing the subscriber’s interest during the sign-up process by asking for as much information as possible, such as their birthday, location, and interests, which might help you send more customized content. Every brand’s subscribers will have different expectations and tolerance thresholds, so testing is key to finding the right balance.
Data quality and hygiene.
Collecting data is only one part of the challenge — you also need to make sure the data is accurate and usable. Start by implementing basic format filters. For example, an email address isn’t valid if it doesn’t include an “@” or “.”. Additionally, avoid accepting common alias addresses, which are also referred to as role accounts (like “info,” “admin,” “sales,” “support,” and so on). Such accounts can present risk because they typically represent a group rather than an individual subscriber. Within a group, expectations and tolerance can vary, which can lead to complaints, inconsistent engagement, unsubscribes, and general confusion. Next, let’s discuss a few solutions to common issues you may run into with your email address data.
Double opt-in (DOI).
DOI is considered the best deliverability practice by most email experts. If you’re having trouble with spam traps or complaints on your welcome emails, DOI is a good way to ensure that the subscriber receiving your emails is the person who actually signed up.
DOI consists of sending a confirmation email to the subscriber’s address who has just signed up for your email program. This email contains a link that must be clicked to confirm consent. If the subscriber doesn’t confirm, they’ll not receive additional emails. You must let new subscribers know you have a double opt-in in place, encouraging them to complete the sign-up before continuing. This method does see a reduction in the number of sign-ups, but those who do sign up tend to be highly engaged and stay for long term. In addition, this method usually results in a much higher ROI for the sender.
Hidden field.
Applying a hidden field to your sign-up form is a great way to differentiate between automated bot sign-ups and human subscribers. As the data field is hidden in the HTML code, a bot will enter data where a human wouldn’t. Using this method, you can build rules to suppress any signup that includes data populated in the hidden field.
ReCAPTCHA.
ReCAPTCHA is a validation method you can use to reduce the chances of a subscriber being a bot instead of a real person. This method has various versions, some of which contain keyword identification or images. Some versions are more effective than others, and the security and deliverability benefits far outweigh any potential negative impact on conversions.
Legal guidelines.
Consult your legal team to interpret local and national laws concerning emails. Remember that email laws vary widely among countries and in some cases among different regions within a country.
- Be sure to collect a subscriber’s location information so that you’re compliant with the subscriber’s country laws. Without that detail, you may be limited in how to market to the subscriber.
- Any relevant laws are generally determined by the location of the recipient, not the sender. You’ll need to know and follow the laws of any country where you might have subscribers.
It’s often difficult to know the subscriber’s country of residence. Data provided by the customer may be outdated, and pixel location may be inaccurate due to VPN or image warehousing, as is the case with Gmail and Yahoo email. When in doubt, it’s usually safest to apply the strictest possible laws and guidelines.
Other non-recommended email list collection methods.
There are many other ways to collect addresses, each with its own opportunities, challenges, and drawbacks. We don’t recommend these in general, since their use is often restricted via provider acceptable use policies. Let’s look at a few common examples, so you can learn their impact and avoid the risks.
Buy or rent a list.
There are many types of email addresses — primary, work, school, secondary, and inactive, to name a few. Addresses collected and shared through buying or renting are rarely primary email accounts, which is where most engagement and purchase activity occurs.
When you buy or rent a list, the best-case scenario is getting secondary accounts that people use to look for deals and offers when they’re ready to shop. This usually results in low engagement levels. In the worst case, the list will be full of inactive addresses, which may now be spam traps. Often, you’ll get a mix of both secondary and inactive emails. In general, the quality of these lists will do more harm than good to an email program. Buying or renting lists is prohibited by Adobe policy.
List append.
These are customers who have chosen to engage with your brand, which is great, but they did so through channels other than email, such as in-store or on social media. They may not welcome an unrequested email and could be concerned about how you obtained their email address since they never provided it. This method risks turning a customer or prospect into a detractor who no longer trusts your brand and may switch to a competitor. This practice is prohibited by Adobe policy.
Trade show or other event collection.
Collecting addresses at a booth or through another official, clearly branded method can be useful. However, many events collect all attendee addresses and distribute them through the event promoter or host. This means the owners of these email addresses never specifically agreed to receive emails from your brand. As a result, they’re more likely to complain and mark your email as spam, and they may not have provided accurate contact information in the first place.
Sweepstakes.
Sweepstakes provide a large number of email addresses quickly. But these subscribers want the prize, not your emails. They may not even have noticed your brand name. As a result, they are likely to complain, mark your email as spam, and rarely engage or make a purchase.
Welcome emails.
Your welcome emails are the biggest foundational factor in driving a successful email program. Consider developing a welcome strategy when creating them.
On average, subscribers who engage with your welcome emails are more than four times likely to continue engaging with future emails if you send a single welcome email. Plus, they’re 12 times more likely to continue engaging if you send a series of three welcome emails.
Regardless of your strategy, subscribers who don’t receive a welcome email or who don’t connect with your welcome message are unlikely to convert into loyal subscribers. A well-planned and carefully crafted welcome email strategy — one that includes the what, when, and who of your messages — creates a positive first impression and sets the stage for long-term subscriber satisfaction.
Here are a few key elements to consider when building your welcome email or series.
Send your message ASAP.
If you’re offering a promotion, your new subscriber is likely waiting on the website to receive the email before making a purchase. A delay of even five to ten minutes can mean a lost sale. Even without a promotion, they’re actively showing interest in your brand. You must engage with them while their interest is piqued, rather than risking an interaction later.
Create strong subject lines and preheaders.
You need to not only thank them for signing up but also to catch their attention and provide a clear incentive to open the email. Use the extra space in the preheader to reinforce your message and highlight the value of engaging with your brand.
Set expectations.
Make it clear that your focus is on creating a positive experience for them. Explain what they can expect from you and how often. Providing an easy way to manage their experience, like a link to a preference center, is also a good idea. Consider adding links to previous content so that subscribers can get a sense of what they're signing up for.
Let them get a feel of your brand.
Every brand has a voice — and you must clearly display yours in your welcome email. This helps new subscribers connect with your brand and prevents surprises with a sudden change in tone in later emails.
Keep it concise.
You have a lot to say and an eager ear in your new subscriber. But your first message should be short, simple, and to the point.
Send a series of emails.
Building a full welcome series (three to five emails) allows you to keep each email concise while still covering all the information you want to share. It also fosters continued interest from your subscribers, leading to positive engagement, a stronger reputation, and improved deliverability.
Get personal.
If you’re doing a welcome email series, apply a personal touch in at least one of them. Use the information you gathered during sign-ups or from the purchase data to personalize their experience, highlighting how you can make it uniquely valuable to them. If you haven’t collected any data yet, use this as an opportunity to show what you could do if given a chance. Then, ask them for the information you need to enrich their experience.
Content best practices for optimal email deliverability.
Content is key. You’ve already read our perspective on relevance, but here are a few additional tips for optimizing your deliverability through content.
- Avoid using an HTML file that's too large. Stay under 100KB to prevent slow deliverability — aim for 60KB to 80KB.
- Use alt tags to your advantage. Alt tags live within the image code and display text when an image isn’t visible or loading. Instead of generic description like “product shot,” use something more compelling like “Buy now and get 30% off.”
- Limit the number of images. Most ISPs block images by default, so make sure your email still captures audience attention. This encourages recipients to enable images later.
Keep volume and strategy consistent.
Sender permanence refers to establishing a consistent sending volume and strategy to maintain a strong ISP reputation. Here's why it matters:
- Spammers often “IP hop,” shifting traffic across multiple IP addresses to avoid reputation issues.
- Consistency signals trust. A steady sending pattern proves to ISPs that you’re a legitimate sender and not attempting to bypass any reputation issues resulting from poor sending practices.
- Long-term consistency is essential. Some ISPs require sustained, reliable behavior before they consider a sender reputable at all.
Internet service provider overview.
Gmail.
Gmail offers limited visibility into your sending practices through Gmail Postmaster tools. This service provides a high-level view of your IP and domain reputation, authentication results, and complaint trends.
Note: Gmail doesn’t display data on all complaints or facilitate a traditional FBL. Instead, it only provides data in certain cases, usually involving both high volumes and complaint rates. While minimizing complaints is critical for deliverability, some complaints are normal. If your complaint rate consistently shows zero, it could point to a reporting issue that requires investigation.
Gmail evaluates engagement differently than most senders. While marketers often define an active or engaged subscriber as someone who opened an email within 30, 90, or 180 days, Gmail looks at how frequently users interact with your messages over time.
For instance, if you send three emails a week for over 90 days, that would be roughly 39 emails. Using the traditional method, if the subscriber opened one of those 39 emails, they’re engaged. However, to Gmail, this means they ignored 38 emails and are not engaged. You can estimate your Gmail users’ engagement by viewing their open activity over the last 10 emails and assigning a score. For example, a subscriber who opened seven of your last 10 emails is more engaged than the one who opened two of those 10. Sending emails less often to those subscribers who are less engaged will help you improve your sending reputation.
Gmail uses different tabs for users to distinguish the types of email. These are “Inbox,” “Social,” and “Promotional.”
Even if email is delivered to the Promotional tab, it’s still considered inbox delivery. Users can customize their view and tabs at any time.
Microsoft is typically the second or third largest provider, depending on your list composition, and it handles traffic slightly differently from other ISPs.
Here’s what you need to know.
Microsoft, including Hotmail, Outlook, and Windows Live.
Microsoft combines all its receiving domains to establish and track sending reputation. This includes Hotmail, Outlook, MSN, and Windows Live, along with any corporate Microsoft Office 365 hosted emails. Microsoft is particularly sensitive to fluctuations in sending volume, so it’s best to apply specific strategies to gradually ramp up or down from large sends instead of allowing sudden volume changes.
Microsoft is also especially strict during the initial days of IP warming, which generally means most emails get filtered in the beginning. While most ISPs consider senders innocent until proven guilty, Microsoft takes the opposite approach and considers you guilty until you prove yourself innocent.
VMG is generally one of the top three domains for most B2C lists. VMG behaves somewhat uniquely, as it typically throttles or delivers emails to the bulk folder when reputation issues arise.
Here’s what you need to know.
Verizon Media Group (VMG), including Yahoo, AOL, and Verizon.
Ongoing monitoring.
Here are some ways to help identify possible issues that might require expert support:
- There’s an observed spike in hard or soft bounces. This could be indicative of a block, blocklisting, or other deliverability issues.
- There’s a noticeable decrease in open and click metrics while delivered rates remain high, which signals potential bulk folder placement.
- There’s a significant increase in complaints. This can be caused by a poor-quality list source.
- There are strategic initiatives that might impact deliverability, such as subscriber acquisition, engagement strategies, seasonal campaigns, or significant changes to frequency and campaign type.
Putting it into practice.
We’ve covered many best practices and deliverability nuances. As you journey forward, keep in mind these four key pillars to success:
- Set proper expectations during sign-up and implement a strong process to prevent bad addresses.
- Provide relevant and timely content.
- Maintain your lists by removing addresses that become invalid.
- Monitor, test, and adjust continuously.
If you’re ever unclear or need assistance with an issue, please contact your Adobe deliverability consultant or expert for help.
Sources
Katherine Haan, "9 Top Email Marketing Statistics," Forbes, February 2, 2026.
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