Email bounce-back errors occur when an email you've sent cannot be delivered successfully to the recipient's inbox.
These errors are typically accompanied by a bounce-back message that provides information about why the delivery failed. Here are some common email bounce-back errors:
- Mailbox Full: The recipient's mailbox is full and cannot accept new messages until the user makes more space available.
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Blocked Sender or Domain:550 5.7.1 - This message has been blocked because the sender's IP address is blacklisted: This indicates that the sender's IP address is listed on a spam or blacklist and emails from that address are being rejected.
- Connection timed out: The server will usually try to resend your message over a 48 hour period. After that timeframe, you should receive a notification in case the delivery has failed.
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Server Unavailable: 421 4.2.0 - Server busy, please try again later: The recipient's mail server is temporarily unavailable due to high traffic or maintenance.
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Domain Not Found:550 5.1.10 - Recipient domain not found: The recipient's domain doesn't exist, or the DNS records are misconfigured.