4.4.7 Message delayed, QUEUE.Expired; message expired
Exchange tried to deliver the message for as long as it is allowed to (two days by default in Exchange Online) and gave up. Each attempt got a temporary error or no answer, so the message waited in the queue and finally expired. The "4.4.7 Message delayed" warning you may have received earlier is the same message still trying; the "message expired" NDR is the end of the road.
What the server replies
550 4.4.7 QUEUE.Expired; message expired
- Sent by
- Microsoft 365
- Type
- PermanentRetry fails
- About
- Connection
- Enhanced code
- 4.4.7
Who sends it
Exchange Online transport queues, as the sending side. The first notice ("delivery is delayed") goes out after a few hours; the final NDR with QUEUE.Expired goes out when the queue timeout is reached.
Why it happens
- The recipient's mail server is down or unreachable.
- The recipient domain's MX record points at a server that does not accept connections, or the firewall drops port 25.
- The recipient server greylists or throttles aggressively and never let the retries through.
- A TLS requirement on either side that the other side cannot meet, causing every connection attempt to fail.
How to fix it
Test the recipient server
Resolve the recipient domain's MX and connect to it on port 25 with an SMTP test. If the connection fails or the banner never comes, the problem is on their side and only their admin can fix it.
Read the earlier delay notice
The delay warning contains the last SMTP response Exchange received. A 421 or 451 tells you the server was throttling; a timeout tells you it was unreachable.
Admin: check connectors and TLS
If the recipient requires TLS through a partner connector, confirm the certificate is valid and the connector's smart host is right. Message trace in the admin center shows the attempts.
Resend once the server is back
Expired messages are not retried automatically. Send again when the recipient confirms their server is up.
Check it yourself
These free tools show the records and connections behind this code for your own domain or server.
Related codes
- 421 Service not available, closing transmission channelThe server is ending the session and wants you to come back later.
- 451 4.7.1 Greylisted, please try again laterThe receiving server has never seen this combination of sending IP, sender address and recipient before, so it refuses the first attempt and remembers the triple.
- 554 5.4.14 Hop count exceeded, possible mail loopThe message passed through more servers than Exchange allows and was discarded as a loop.
Sources
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