Mail Delivery Failed – What It Means and What to Do

A 'Mail Delivery Failed' bounce-back email means your message wasn't delivered. Here's what the error codes mean and what to do next.

Frequently asked questions

Does 'Mail Delivery Failed' mean my email was hacked?
Rarely. The most common cause is a simple typo in the recipient's address, a full mailbox, or a temporarily unavailable mail server. If you receive delivery failure notices for emails you didn't send, that's a different situation worth investigating.
Will the recipient ever get my email?
It depends on the error type. A 'permanent' failure (5xx error code) means the message will never be delivered — you'll need to resend to a corrected address. A 'temporary' failure (4xx) means the server will keep retrying for 24–72 hours before giving up.
Is the bounced email lost?
Your original email is still in your Sent folder. The delivery failure notice just tells you the recipient's server rejected it. You can copy and resend to a corrected address at any time.
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