Why did my email bounce back? How to read the error
When an email bounces, you get an automatic reply, often titled "Undeliverable" or "Delivery Status Notification". It looks scary, but it usually tells you exactly what went wrong if you read it carefully.
Look for the plain-English line
Near the top of the bounce message there is usually a sentence explaining the problem. Ignore the long strings of technical text at first and look for words such as "address not found", "mailbox full" or "message too large".
Common causes and what to do
- Address not found or does not exist: The address is probably mistyped, or the person has left. Check the spelling, including dots and the part after the @ sign. Ask the person to confirm their address another way, such as by phone.
- Mailbox full: Their inbox has no space. Try again later or contact them another way.
- Message too large: The attachments are too big. Use a sharing link instead. See our guide on attachments that are too large.
- Blocked or rejected as spam: The receiver's system did not trust the message. Avoid very short messages with only links, and ask the person to check their junk folder and to add you as a safe sender.
- Temporary problem or delayed: Sometimes the message is still trying. You will usually be told it will keep retrying. Wait before sending again.
What to try
- Re-read the address you typed, or find an earlier message from that person and reply to it.
- Resend the email.
- Try a shorter message without attachments, as a test.
- If it bounces again, copy the exact wording of the error somewhere safe.
A warning
If you get a bounce for an email you never sent, someone may be pretending to be you. Do not click links in the bounce. Change your password using the provider's official sign-in page and turn on two-step sign-in.
When to get more help
Contact us if the error mentions words such as "SPF", "blocked" or "blacklisted", if business emails keep bouncing to the same domain, or if you see bounces for emails you did not send. Please send us a screenshot of the full error.