How can I handle a high bounce rate with emails that I send using Amazon SES?

Last updated: 2020-09-25

The bounce rate of my Amazon Simple Email Service (Amazon SES) account is higher than normal. Or, my bounce rate spiked or increased suddenly. It's putting my account at risk for an account review or a sending pause. How can I identify what's causing the increase in bounce rate? What can I do to prevent a high bounce rate?

Resolution

Identify the cause of the increase in bounce rate

To stop the bounce rate from increasing, you must identify the email addresses that are causing the bounces. To do this, you can configure bounce notifications using an Amazon Simple Notification Service (Amazon SNS) topic. From the SNS notifications, find the email addresses that are resulting in bounces.

To identify what's causing the increase or spike in bounce rate, review the following fields in the message body of the Amazon SNS bounce notifications:

  • bounceType: A Transient bounce type is a soft bounce, which is a temporary failure or rejection that can generally be retried. A Permanent bounce type is a hard bounce, which is a persistent delivery failure or rejection from the receiving mail server. Hard bounces aren't retried, so your recipient doesn't receive the email message.
  • diagnosticCode: The code in this field provides more information on what's causing the bounces.

Stop sending email to the addresses that are increasing your bounce rate

After you identify the email addresses that are resulting in bounces, you must stop sending messages to those addresses so that your bounce rate doesn't increase further. Be sure to remove the email addresses from your email recipient lists.

Additionally, confirm that your Amazon SES account is enabled for an account-level suppression list. When enabled, this feature can prevent your account from sending email to addresses that result in hard bounces or complaints, which can help prevent an increasing bounce rate.

Resolve the root cause of the increase or spike in your bounce rate

After you take the immediate action to stop sending emails to addresses that result in bounces, you must identify and resolve the root cause of the increase in bounces.

Some of the most common reasons for an increase or sudden spike in bounce rate include:

  • You can get a spike in bounces if you send messages to an email list that contains recipients with invalid mailboxes. This can happen if you use an incorrect or out-of-date list of recipients. You must remove any invalid email addresses from the list before sending messages again. For more information on managing email lists, see Amazon SES best practices: Top 5 best practices for list management.
  • Based on your reputation metrics, mailbox providers can block the IP address that you're sending email from. If there's a large number of subscriber complaints, then a mailbox provider might block your messages. Follow the guidance that you find on the mailbox provider's postmaster site to remove the block.
  • Mailbox providers can use a third-party blocklist to filter email. If you continue to send messages to a mailbox after your messages are blocked, then your bounce rate can increase. You can contact the mailbox provider or blocklist provider to get information on why your messages are blocked. After you're removed from a blocklist, you must address the issues and change your sending habits accordingly. Otherwise, you risk getting blocked again and getting more bounces. Be sure to review the policies for removing Amazon SES IP addresses from IP blocklists.

After you identify the root cause of the increase in bounces, be sure to review the design of your sending application because the design can impact your bounce metrics. For example, if your application sends a confirmation email to the user when they sign up and the user enters an invalid email address, then the confirmation email results in a hard bounce. Additionally, if you set up your application to retry sending emails whenever there's a failure and there are issues on the recipient's mailbox, then you continue to get bounces. For more recommendations on mechanisms that you can implement in your application for successful sending metrics, see Building and maintaining your lists.

For more information on ways to keep a low bounce rate, see What can I do to minimize bounces?

Implement a bounce and complaint monitoring system

To avoid a high bounce rate, or to address increasing bounces quickly, it's a best practice to implement a bounce and complaint monitoring system.

Use the Amazon SES reputation dashboard to check your account's bounce and complaint rates. Set up notifications about bounces and complaints using email feedback forwarding, Amazon Simple Notification Service (Amazon SNS), or Amazon SES event publishing.

For threshold-based notifications, set up Amazon CloudWatch alarms for your bounce and complaint rates. For threshold-based pauses in email sending, use CloudWatch and AWS Lambda to automatically pause your email sending at a certain bounce or complaint rate. It's a best practice that you maintain a bounce rate under 5% and a complaint rate under 0.1%.

With a monitoring system and notifications, you can also implement a solution to automate how bounces are processed, such as in the following examples: