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SMTP & bounce error code lookup
The raw code, what it actually means, and what to do about it. No paraphrasing.
Permanent (5xx) - don't retry
- 550 5.1.1Mailbox does not exist
- 550 5.7.1Message rejected as spam or policy violation
- 551 5.1.6Recipient no longer on server
- 552 5.2.2Mailbox full (permanent)
- 552 5.3.4Message too large
- 553 5.1.2Invalid recipient address
- 554 5.7.1Message rejected due to policy
- 554 5.7.9Message not accepted for policy reasons (authentication failure)
- SES: General (Permanent)AWS SES generic permanent bounce
- SES: NoEmail (Permanent)No mailbox by that name
- SES: Suppressed (Permanent)Recipient on account-level suppression list
- SES: OnAccountSuppressionList (Permanent)Blocked by SES account-level suppression list
- SES: AttachmentRejected (Permanent)Attachment type not allowed
- SES: Complaint (feedback loop)Recipient marked the message as spam
Transient (4xx) - safe to retry
- 421 4.3.2Service not available, closing transmission channel
- 421 4.7.0Temporary policy rejection
- 450 4.2.1Mailbox temporarily unavailable
- 450 4.7.1Greylisting
- 451 4.3.0Local error in processing
- 451 4.4.1No answer from host / connection timeout
- 452 4.2.2Mailbox full (temporary)
- 452 4.3.1Insufficient system storage
- SES: MailboxFull (Transient)Recipient mailbox is full
- SES: MessageTooLarge (Transient)Message exceeds receiving server's size limit
- SES: ContentRejected (Transient)Message content rejected by the receiving server
- 421 4.7.28Rate limited due to reputation (Gmail-style)
- 450 4.7.0Temporary access denied