Understanding email bounces
Analyze and resolve bounced emails for increased deliverability.
Email bounces are a common issue with email campaigns. Knowing how to address and prevent them is important for maintaining the health of your email campaigns and sender reputation.
What are email bounces?
An email bounces happens when an email service provider (ESP) attempts to deliver an email to the recipient’s email server, but the delivery fails or is rejected. This results in an automated bounce message, which indicates the error, being sent back to the sender. There are two types of email bounces:
Soft bounces (4.X.X Codes): These are temporary issues, meaning your email could still be delivered after a retry. Soft bounces are commonly due to the recipient's inbox being full or a temporary problem with the recipient’s server.
Hard bounces (5.X.X Codes): These are permanent failures, meaning the email will not be delivered no matter how many retries are attempted. Hard bounces are typically due to content, strict policy enforcement, or because the email address is invalid, non-existent, or blocked.
Reading bounce reports
Most ESPs or email systems will generate a bounce report when an email is undeliverable. These reports contain important details like the recipient's email address, the time the bounce occurred, and an error code that explains why the bounce happened.
A typical bounce report might look like this:
Recipient: [email protected]
Status: 5.1.1 (Bad destination mailbox address)
Diagnostic-Code: smtp; 550 5.1.1 User unknown
This report tells us that email delivery failed permanently because the email address of the recipient ([email protected]) does not exist.
Resolving bounced emails
Resolving bounced emails depends on the type of bounce and the specific error code associated with it.
4.X.X codes (temporary failures)
Wait and monitor: Since these are temporary issues, you often don’t need to take immediate action. Monitor the bounce reports to see if the message eventually gets through.
Retry sending: Your email provider will typically retry sending the email, but if it continues to bounce you may want to wait a few hours or days and try again manually.
Contact the recipient: If the bounce persists, try reaching out to the recipient through another channel (like phone or social media) to let them know their inbox is full or their server is having issues.
5.X.X codes (permanent failures)
Correct invalid addresses: For issues like a 5.1.1 error (non-existent email), verify that the recipient's email is accurate. If possible, reach out to the person to obtain their correct address.
Remove or update old addresses: If an email address is outdated or inactive, remove it from your mailing list to prevent further bounces. Keeping a clean, updated list is essential to maintaining a positive sender reputation.
Check spam filters and policies: For 5.7.1 errors (policy rejections), check whether your emails are being flagged as spam. Make sure your content follows best practices, such as avoiding spammy subject lines or attaching large files.
Authenticate your domain: Some bounces happen because the recipient’s server doesn’t trust the sender's email domain. Implementing email authentication protocols like SPF, DKIM, and DMARC can improve deliverability.
Work with your email provider: If you're seeing recurring bounces from multiple addresses on a single domain, it could be that the recipient’s server is blocking emails from your domain. Contact your email service provider (Google or Microsoft) or the recipient's IT department to resolve the issue.