When an email cannot be delivered, you get a bounce-back message explaining why. These can look cryptic, but they usually point to a clear cause. This guide helps you read them and fix the common problems.
Two kinds of bounce #
- Hard bounce: a permanent failure, such as an address that does not exist.
- Soft bounce: a temporary problem, such as a full mailbox or a server briefly unavailable.
Common bounce reasons and fixes #
- “User unknown” / “no such address”: the address is wrong or no longer exists; check the spelling.
- “Mailbox full”: the recipient’s inbox is full; they need to clear space, or try later.
- “Message rejected as spam”: improve your authentication (SPF, DKIM, DMARC) and content.
- “Relay access denied”: often an outgoing server or authentication setting on your side.
How to read a bounce message #
Look for the status text and any error code near the top. It usually names the failing address and the reason in plain language, which tells you whether the issue is the address, the recipient’s server, or your own setup.
If your own mail keeps bouncing #
- Confirm the recipient address is correct.
- Check your outgoing (SMTP) settings and authentication.
- Make sure your domain’s SPF, DKIM, and DMARC are set up.
Need help? #
If you cannot make sense of a bounce message, our support team can interpret it and help you fix it. Start a live chat.
