Common mail bounces and their description
Hard bounce
The response from the remote server was:
550 5.7.1 No such user! 1683454980-0NPfrE8P9Cg0-eRlBSO3hCauses for a hard bounce:
- The recipient's email address does not exist.
- The recipient's email server blocked the delivery completely.
Soft bounce
Soft Bounce - usually indicates a temporary problem with mail delivery.Causes for a soft bounce:
- The mailbox is full.
- The mailbox is configured incorrectly.
- The mailbox is inactive.
- The recipient's email server is not available.
- Too many emails have been sent to the recipient's mail server in a certain period of time.
- The message is too big.
- The domain name does not exist.
- Post blocked due to content content.
- The message does not comply with the policy of the receiving server.
- The message does not meet the DMARC requirements for authentication.
- The message does not meet anti-spam requirements.
- The message does not meet antivirus requirements.
- E-mail cannot be transferred between mail servers.
- Email cannot be relayed for unknown reasons.
Bounce classification
| Name | Description | Category |
|---|---|---|
| Undetermined | Reply code could not be identified | Undetermined |
| Invalid Recipient | Recipient is invalid | Hard |
| Soft Bounce | The letter was rejected | Soft |
| DNS Failure | Message was returned due to a DNS error | Soft |
| Mailbox Full | The recipient's mailbox is full | Soft |
| Too Large | Message was rejected due to size | Soft |
| Timeout | Message timed out | Soft |
| Generic Bounce: No RCPT | Failed to determine message recipient | Hard |
| Generic Bounce | Message rejected for unknown reasons | Soft |
| Mail Block | Message has been blocked by recipient | Block |
| Spam Block | Your message was considered spam by the recipient | Block |
| Spam Content | Your message was considered spam by the recipient | Block |
| Prohibited Attachment | Message was rejected due to attachment | Block |
