451 4.4.2: Connection timed out
451 4.4.2 means the connection between the sending and receiving servers timed out or dropped before the message was fully delivered. Gmail closes idle or slow connections with this code. It is temporary: the sending server retries on a new connection, and it only becomes a bounce if every retry fails.
The exact messages
Gmail / Google Workspace
451 4.4.2 Timeout - closing connection.
Any mail server (RFC standard meaning)
4.4.2 Bad connection
Why it happens
- A slow or unstable network path between the two servers.
- A sending server that pauses too long between SMTP commands, for example while scanning a large message.
- A large attachment on a slow uplink.
How to fix it
- Let the server retry; an occasional timeout is normal on the internet.
- If a self-hosted server sees them constantly, check its network, DNS resolution speed and outbound bandwidth.
- Keep cold emails small: no attachments and few images.
If you send cold email
Not a reputation signal. Occasional 4.4.2 retries on outreach are harmless; a steady stream from your own server points at its network, not at your domain.
How WarmHawk handles it
A Google Workspace or Microsoft 365 mailbox connected to WarmHawk sends through the provider’s own servers, which already use TLS. A temporary failure is retried with backoff (30 minutes, then doubling, capped at 48 hours) and the lead is suppressed after 4 attempts instead of being retried forever. How WarmHawk works →
Related bounce codes
- 4.4.5Server busy, try again later
- 4.4.7Message expired in the queue
- 4.3.0Mail server temporarily rejected the message
Sources, checked 2026-09-29: Google Workspace: Gmail SMTP errors and codes · RFC 3463: Enhanced Mail System Status Codes. Have a different bounce? Paste it into the decoder →
Questions
4.4.2 questions
What does 4.4.2 mean?+
451 4.4.2 means the connection between the sending and receiving servers timed out or dropped before the message was fully delivered. Gmail closes idle or slow connections with this code. It is temporary: the sending server retries on a new connection, and it only becomes a bounce if every retry fails.
Is 4.4.2 a temporary or permanent error?+
Temporary. The sending server keeps the message and retries it for a while. It only becomes a bounce if every retry fails before the message expires.
How do I fix 4.4.2?+
Let the server retry; an occasional timeout is normal on the internet. If a self-hosted server sees them constantly, check its network, DNS resolution speed and outbound bandwidth. Keep cold emails small: no attachments and few images.