Microsoft (Outlook.com and Microsoft 365) · permanent error
550 5.7.128: transport rules redirected the message too many times
Transport rules in one or more organizations kept redirecting the message, and Exchange Online stopped it at the redirection limit.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.128
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- Either side, depending on the cause. Start with the checks below that are yours.
- What the server says
550 5.7.128 TRANSPORT.RULES.RejectMessage; Transport rules loop count exceeded and message rejected
What it means
Exchange Online limits how many times transport rules can redirect a single message, and it tracks the count in the X-MS-Exchange-Transport-Rules-Loop header, which stays on the message across organizations. Microsoft's example is a chain of organizations whose rules each redirect the same message to a user in the next one. Once the limit is exceeded, the message is dropped and the original sender gets 550 5.7.128.
Common causes
- A transport rule redirects messages to a recipient in another organization whose own rule redirects them onward or back.
- Several redirect rules in a chain together exceed the limit.
How to fix it
- 01Forward the report to your admin.
- 02Admins: use message trace to find the mail flow rules with a redirect action that applied to the message.
- 03Change or scope the rules so a message is redirected only once, coordinating with the other organization's admin if its rules are involved.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Exchange Online limitslearn.microsoft.com
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce