Microsoft (Outlook.com and Microsoft 365) · permanent error
554 5.6.0: attachment scan timed out under a transport rule
A Word or Excel attachment could not be scanned in time by a transport rule set to defer on failure, so the message was returned.
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- Permanent (5xx)
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At a glance
- Code
- 554 5.6.0
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
554 5.6.0 Invalid message content
What it means
Microsoft documents 554 5.6.0 Invalid message content for a message with an Excel (.xlsx) or Word (.docx) attachment sent from Microsoft 365. Two conditions combine: a transport rule has the option Defer the message if rule processing doesn't complete turned on, and text extraction timed out while the attachment was being inspected. The rule cannot finish, so the message is not delivered.
Common causes
- A transport rule has Defer the message if rule processing doesn't complete enabled.
- Text extraction from the attachment timed out during scanning.
How to fix it
- 01As a workaround, password-protect the message before sending it again.
- 02Admins: turn off Defer the message if rule processing doesn't complete on the rule that has it.
- 03Review the message and a message trace for more detail on where processing stopped.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 550 5.6.0Moderation fails without an expiry policy tag.A message to a moderated group failed because the approval agent needs a retention tag that the organization has not created.
- 5.6.0Message content problem, unspecified.Something about the content of the message made it undeliverable, and the server did not say exactly what.
- 554Transaction failed.The server permanently refused the transaction, often after receiving the message data or straight away when the connection opened.
5.6.0 at other providers
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