Email marketing Mail bounces

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    bounce mail

Common mail bounces and their description​

Hard bounce​

The response from the remote server was:
550 5.7.1 No such user! 1683454980-0NPfrE8P9Cg0-eRlBSO3h
Hard Bounce - Indicates a permanent reason why the email could not be delivered.

Causes 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​

UndeterminedReply code could not be identifiedUndetermined
Invalid RecipientRecipient is invalidHard
Soft BounceThe letter was rejectedSoft
DNS FailureMessage was returned due to a DNS errorSoft
Mailbox FullThe recipient's mailbox is fullSoft
Too LargeMessage was rejected due to sizeSoft
TimeoutMessage timed outSoft
Generic Bounce: No RCPTFailed to determine message recipientHard
Generic BounceMessage rejected for unknown reasonsSoft
Mail BlockMessage has been blocked by recipientBlock
Spam BlockYour message was considered spam by the recipientBlock
Spam ContentYour message was considered spam by the recipientBlock
Prohibited AttachmentMessage was rejected due to attachmentBlock


  • #2
Thank you very much, this post is good for identifying bounce messages.


  • #3
Thank you very much!


  • #4
very usefull!


  • #5
nice info!