4.4.0: network or routing problem, unspecified
Something went wrong with the network or the routing between mail servers, without a more specific explanation, and delivery is usually retried.
- Standard
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 4.4.0
- Provider
- Standard SMTP codes
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- Either side, depending on the cause. Start with the checks below that are yours.
- What the server says
4.4.0 Other or undefined network or routing status
What it means
X.4.x codes report on the delivery infrastructure: connections, DNS and routing. Detail 0 means the problem did not fit a more specific code. Most network problems pass, so the code is usually seen as 4.4.0: the sending server, often your own provider's, could not reach the next server or resolve its name, and keeps retrying. A 5.4.0 means it gave up on this route. Because X.4.x codes are often written by the sending side about its own attempts, the text after the code (a DNS error, a timeout, the address it tried) is the best clue to where the path broke.
Common causes
- A DNS lookup for the recipient's mail servers failed or returned nothing usable.
- The connection to the receiving server failed or dropped.
- A routing rule on a server along the way sent the message nowhere.
How to fix it
- 01Let the queue retry; most network problems clear without action.
- 02Run an MX lookup on the recipient domain to confirm its mail servers resolve.
- 03If you run the sending server, check its DNS resolver and its outbound connections on port 25.
- 04If the message stays queued, contact the recipient's administrator with the error text.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 4.4.1No answer from the receiving server.The sending server tried to connect to the receiving server and got no answer, so it keeps the message and tries again later.
- 4.4.3DNS or directory lookup failed.The message could not be passed on because a directory server, most often DNS, did not answer; the lookup and the delivery are retried.
- 5.4.4No route to the recipient domain.The mail system could not work out where to send the message next, because DNS gave no usable mail server for the recipient domain.
- 4.4.7Delivery time expired.The message stayed undelivered for too long, usually because every retry failed, so the server gave up on it or warned that it is delayed.
Further reading
All 105 standard codesEvery code in the wikiPaste your own bounce