Gmail / Google Workspace error guide

Gmail / Google Workspace SMTP 552 5.3.4: Message Or Header Size Limit

Gmail / Google Workspace SMTP 552 5.3.4 usually means message size. Learn whether to retry, suppress the recipient, or fix sender setup.

Quick summary

Primary code
552 5.3.4
Provider coverage
Gmail / Google Workspace
Primary action
Fix sender setup

How to handle 552 5.3.4

Match the provider, SMTP stage, endpoint, and diagnostic wording first, then use the checks below to decide whether to retry, suppress the recipient, or fix sender setup.

Gmail 552 5.3.4

Message size

Fix sender setup

Message size means the receiving provider rejected the message for a provider-specific reason. Use the diagnostic text before deciding on retries or suppression.

Decision

Do not retry unchanged. Fix the sender setup first.

Confidence: high. Recipient validity: unknown.

Match this reply

SMTP stage
End of DATA
Endpoint
Inbound MX
too largesize limitheaderSubject:attachment

Start here

  1. 1

    Reduce attachment size and header size before retrying.

  2. 2

    Move large files behind a link instead of attaching them directly.

Confirm the cause

  1. Check total message size, attachment size, and header size.
  2. Replace large attachments with links and compress inline images where possible.
  3. Retry only with a smaller message or a recipient path that accepts the size.

App handling

  • Treat this as a sender setup incident, not a bad recipient.
  • Hold similar mail for the same sender domain or provider until the fix is verified.
  • Retry after a fresh single-recipient test succeeds.

Avoid

  • Do not retry unchanged in a loop.
  • Do not suppress the recipient unless the text explicitly says the mailbox is invalid.
  • Do not treat a permanent SMTP code as proof that the address is bad; policy and routing failures can also be permanent.
Common causes
  • The message or attachment exceeds the provider's size limit.
  • Large headers, inline images, or tracking metadata push the message over the limit.
  • The recipient-side service has a lower message-size cap than the sender expects.
Developer details
Fields to log
raw SMTP replyremote MX or hostSMTP stagereply codeenhanced codeprovidermatched rule idrecipientsending domaindecisiontimestamp
Classifier evidence
Specific cause
message or header size limit
Evidence
official
support.google.com source 1

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