Enhanced SMTP status code · RFC 3463 · IANA
4.4.316 Connection refused [Message=Socket error code 10061]
Microsoft 365 cannot connect to the recipient's server because of a network problem on that side.
- Class: Temporary failure
Class 4: a persistent transient failure. The message was fine, but a passing condition delayed or stopped delivery; a later attempt may succeed (RFC 3463 §3.1). The sending server retries on its own for a while.
- Subject: X.4 · Network and routing
Network and routing status (DNS included); under the control of the destination's or an intermediate server's administrator.
How 4.4.316 appears at providers
The exact text from the provider's documentation, as you see it in the bounce, and what it means.
Microsoft 365 / Exchange Online
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4.4.316
Connection refused [Message=Socket error code 10061]
Microsoft 365 cannot connect to the recipient's server because of a network problem on that side. Check with SMTP server check.
What you can check here
Have the whole error message?
Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026