Optimizing Email Deliverability: A User-Centric Approach to List Management and Monitoring

Targeting active and engaged users is one of the most effective ways to maintain a strong sender reputation. This time-tested best practice is known as confirmed opt-in (also known as double opt-in). This process is quick to implement and highly effective. When a user signs up for a newsletter or special offer using their email address via a form on your website, you should verify the legitimacy of the email address by sending a verification email to the provided address and asking the requestor to click a link that confirms their consent to receive your emails. By clicking this link, the email address owner explicitly provides their consent to receiving email notifications. Once the recipient verifies the request, you then add their email address to your active mailing list. Most users are now familiar with this type of verification, and legitimate recipients will have no trouble confirming their interest.

Our guidance regarding the confirmed opt-in best practice has evolved due to the prevalence of online bots and bad actors. To maintain a strong sender reputation, we now recommend protecting your web sign-up forms with a CAPTCHA (or similar mechanism). This helps ensure the requests to join your mailing list come from a real human, not a ‘bot or some form of automation or deception. Only after a requestor proves they are human would you accept their email address and then send the verification email. This additional layer of protection prevents bots and bad actors from signing up users without their consent.

CAPTCHA has become a foundational element of the double opt-in process. Protecting the sign-up process with a CAPTCHA will limit the number of unsolicited confirmation messages sent to users, and subsequently reduce the chances of mailbox providers labeling the confirmation messages as spam. If the confirmation messages are blocked by MBPs, then the double opt-in process simply isn’t viable.

Figure 1: AWS WAF CAPTCHA examples.

By verifying the legitimacy of your email recipients upfront through confirmed opt-in, you will reduce the number of invalid recipient bounces associated with fake emails, typographical errors, and illegitimate sign-ups by bad actors and bots. This is crucial, as these types of invalid addresses can negatively impact your sending reputation.

Figure 2: A diagram showing the ideal confirmed opt-in architecture to limit risk of bot abuse.

1. Adding a CAPTCHA on the sign-up web form proves that a human is interacting with the sign-up process.
2. Ensuring the link is clicked proves that a person or application with access to the mailbox was able to click the link.
3. Requiring the recipient to enter the correct one-time passcode, commonly referred to as OTP, into the web form proves that the human requesting sign-up is the same as the person confirming the sign-up
4. Monitoring bounce, complaint, and delivery delay events proves that the email address is valid and that there are not recipients who are marking the confirmation messages as spam.
   • Use a subdomain for sending the confirmation messages to limit reputational impact on deliverability in case there are signs of web form abuse
   • If there are signs of web form abuse, give recipients an easy option to report abuse so that they don’t mark the messages as spam.

Confirmed opt-in ensures you only send to subscribers who have explicitly consented to receive your messages. By honoring their subscription preferences, you further reduce the chances of complaints. Providing recipients with an easy, one-click unsubscribe option is crucial, as it demonstrates your commitment to respecting their communication preferences.

Many successful senders capitalize on the verification window by immediately sending a welcome email. This offers two key benefits:

Carefully Monitor Bounces, Complaints, and Delivery Delays

Update: Monitoring these metrics has become substantially more important due to recent changes by mailbox providers. As of February 2024, Google, Yahoo, Microsoft and other MBPs now require all bulk-senders to keep their spam complaint rates below 0.3%. These MBPs explain that maintaining a low spam complaint rate benefits both senders and recipients by enhancing email deliverability, preserving sender reputation, and fostering a more positive user experience for their in-box subscribers.

To fully understand the latest industry standards and requirements, we recommend:

• Read the Overview: Get a quick grasp of the key compliance guidelines
• Watch the Webinar: Dive deeper into the specific details and best practices presented by the AWS and Gmail teams.

Amazon SES provides real-time feedback on bounces, complaints, and delivery delay events through its event publishing feature. This enables you to quickly identify and remove problematic email addresses, ensuring you maintain a clean and healthy subscriber list.

If you receive a hard bounce or a complaint, it’s essential to remove that email address from your list and investigate the root cause. For example, a sudden increase in bounce and/or complaint rates for new subscriptions may indicate an issue with fake sign-ups. In such cases, leveraging confirmed opt-in (the BCP, or best current practice, of list building) can help discourage this problem. By using a separate domain for your signups and OTPs, you can distinguish bounces and complaints from sign-ups and other transactional message types, in comparison to your marketing or promotional messages.. More can be found here.

Amazon SES’s Virtual Deliverability Manager (VDM) is an Amazon SES feature that helps senders identify deliverability trends and potential deliverability issues without the need to build additional dashboards. VDM provides deep insights into your sending data and offers actionable recommendations to improve deliverability. VDM helps monitor bounce rates, complaint rates, and other key performance indicators (KPIs) to support email delivery success metrics. VDM allows senders to explore deliverability issues, including the ability to drill down from account level statistics all the way down to the individual message level. This will help identify problematic emails without needing to sift through all of your deliverability data. Key capabilities include:

• Bounce Details: Use VDM to identify bounced emails by recipient addresses, timestamps. and SMTP response codes. These are received directly from the recipient mailbox providers. Users can then group emails by bounce type (permanent and transient) and recipient domains to analyze and take correct action before before smaller deliverability events like message delays turn into larger problems like messages being blocked by the MBPs.
• Complaints: Identify recipients who marked emails as spam so they can be removed from the active mailing list.
  • Note: for metric tracking tied specifically to Gmail recipients, customers should also be monitoring Google Postmaster Tools to track their reputation and keep their spam complaint rates low.
• Delivery Metrics: Monitor delivery attempts, retries, and success to make informed decisions based on real-time data to continuously improve deliverability.

VDM proactively flags potential problems like bounces and complaints that could harm your sender reputation and delivery rates. By addressing these issues early, you can verify that your emails consistently reach the inbox, instead of the spam folder.

While VDM is a paid service for Amazon SES customers, there is a free tier that provides a flexible way to test out the tool without any expenses or commitments.

To dive deeper into VDM consult these resources:

• Explore the Improve Email Deliverability with VDM: resource to learn about the feature’s capabilities and benefits.

For additional guidance on SES bounce and complaint monitoring, refer to the following resources:
Amazon SES Documentation:

• Monitoring Your Amazon SES Sending Activity
• Understanding Email Deliverability in Amazon SES

Amazon SES Blog Posts:

• Analyzing Amazon SES event data with AWS Analytics Services
• Handling Bounces and Complaints
• Improve email delivery rates with email delivery and engagement history for every email
• Amazon SES – How to track email deliverability to domain level with CloudWatch

Proactively Remove Non-Engaging Subscribers

Imagine a scenario where a subscriber signs up for your email list but never engages by opening or clicking through your messages. This lack of activity could indicate the subscriber’s loss of interest. To address this, we recommend you set a reasonable timeframe for engagement based on your industry standards (e.g., 6 months of no opens or clicks). However, this timeframe may need to be adjusted depending on how regularly you send emails to your subscribers. For instance, if you send a daily newsletter, a 6-month period of inactivity may be too long before removing the subscriber. Conversely, if you only send monthly updates, a 6-month window may be more appropriate. The key is to find the right balance – remove subscribers who have clearly lost interest, but don’t be too hasty in culling your list if they simply don’t engage as frequently as your regular email cadence. By tailoring the engagement timeframe to your specific email frequency, you can ensure your subscriber list remains active and engaged.

Consider a “Win-back” Email Campaign

Before removing completely inactive subscribers from your list, consider sending them a special “win-back” email. This final attempt to re-engage them can be an effective strategy to win-back valuable subscribers. The win-back email should have a clear and compelling call-to-action, encouraging recipients to re-engage with the messages you are sending to them. This could include updating their preferences or confirming their interest in your messages. By giving these subscribers another chance, you may be able to reactivate a portion of your list and retain those recipients. However, if the win-back email fails to elicit a response, it’s best to remove those addresses from your active mailing list to maintain a healthy, engaged subscriber base.

Even subscribers who originally opted in through a confirmed double opt-in process can become inactive over time. Occasionally these email addresses are abandoned and can be converted into spam traps by the domain owner. Spam traps are email addresses used by organizations to identify senders who may not be following best practices for list building and long-term list hygiene. If you continue to email these inactive addresses, several negative consequences can occur. our domain could be at risk of generating poor reputation at a mailbox provider, or end up on a real-time blocklist, which may impact deliverability to multiple mailbox providers. In some cases, this could result in your Amazon SES service being suspended.

Proactively removing non-engaging subscribers is the only way to avoid these potential pitfalls and maintain a strong sender reputation.

For a deeper dive into the topic, refer to the following resources:

Removing inactive subscribers is a powerful complement to your confirmed opt-in practices, helping you maintain a healthy, high-performing email list.

Make Unsubscribing Easy to Maintain a Clean, Compliant List

Update: Providing recipients with clear, easy-to-use unsubscribe options has become even more crucial due to recent changes by major email providers.

As of February 2024, Google and Yahoo now require all bulk email senders to include a prominent unsubscribe link within their messages. In June 2024 the implementation of one-click unsubscribe headers (as defined by RFC 2369 and RFC 8058) also become mandatory across the industry.

Figure 4: A diagram of one-click unsubscribe flow.

The new industry wide bulk sender requirements ultimately benefit both senders and recipients by:

• Reducing Spam Complaints – Easy unsubscribe options decrease the likelihood of frustrated recipients marking your emails as spam. This helps maintain a positive sender reputation.
• Improving Sender Reputation – A clean email list with engaged and consented subscribers keeps your sender reputation healthy, ensuring your messages consistently reach the inbox rather than the spam folder.

It is critical you respect your audience’s wishes as they relate to your email sending. When you offer recipients a straightforward, easy unsubscribe path to manage their communication preferences, it will allow you keep your email lists clean and compliant which helps you maintain a strong sender reputation. Many regions, including the US, Canada, and parts of Europe and Asia, have adopted laws requiring senders to provide clear, accessible unsubscribe mechanisms. Adhering to these regulations helps you avoid potential legal issues related to your sending and local messaging laws.

Amazon SES provides a basic, subscription management capability that supports the Bulk Sender Requirements as outlined in the SES documentation. Some SES customers have opted to develop & deploy their own custom, more comprehensive systems, to process end-user unsubscribe requests. For a deeper dive into the topic, refer to the AWS blog post Using one-click unsubscribe with Amazon SES.

Build Trust by Growing Your List Organically

Avoid the Temptation of Shortcuts

• Spam Complaints: Recipients who never consented to receive your emails are much more likely to mark them as spam, harming your sender reputation.
• Legal Issues: Many countries, especially with the new <0.3% spam rate requirement, have strict laws prohibiting the use of non-consensual email lists.
• Unsubscribes and Lost Trust: Sending unwanted emails can result in high unsubscribe rates and damage your brand’s reputation.

Focus on Building Your List Organically

Land in Inboxes, Not Spam Folders: The Power of Streamlined List Management