550 5.7.367: forwarded mail rejected by the next hop
A message Microsoft 365 forwarded or relayed was refused by the next server, often a third-party gateway, because it left from Microsoft's relay pool.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.367
- 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
550 5.7.367 Remote server returned not permitted to relay
What it means
When Microsoft 365 forwards or relays a message for an external sender, it picks an outbound pool. If email authentication failed as the message came in, it may go out from a relay pool that is not part of Microsoft 365's published SPF record or outbound IP ranges. Downstream gateways, such as Proofpoint or Barracuda, then do not treat Microsoft 365 as the sender and refuse to relay, which comes back as 550 5.7.367, often followed by the gateway's own 554 5.7.1 Relaying denied. The failures are intermittent, mostly with automatic forwarding and multi-hop routes.
Common causes
- SPF failed or soft-failed when the message entered Microsoft 365, often because a third-party gateway sits in front of it.
- The forwarded message's sender is not in an accepted domain of the tenant.
- The route has several hops or uses automatic forwarding.
How to fix it
- 01If your MX points to a third-party service or an on-premises server, turn on Enhanced Filtering for Connectors so SPF is evaluated correctly for inbound mail.
- 02If the sender domain is yours, add it as an accepted domain in Microsoft 365.
- 03Reduce relay hops and automatic forwarding where you can.
- 04Confirm the cause in message trace: affected messages show OutboundIpPoolName as RegularRelayOutboundPool.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Forwarded or relayed email messages from Microsoft 365 are rejected with error 5.7.367learn.microsoft.com
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
Related codes
- 5.7.1Unable to relay.The receiving system refused to pass the message on because it is not the final destination for the recipient domain.
- 550 5.7.23SPF violation on outgoing mail.The destination checked SPF on mail sent from your Microsoft 365 organization and rejected it, which points to a problem in your SPF setup.
- 5.7.520Automatic external forwarding blocked.Exchange Online stopped an automatically forwarded message because the organization's outbound spam policy blocks forwarding to external addresses.
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce