SMTP error 441
No answer from host — a misread of 4.4.1, or an AuthSMTP quota code.
Updated Jul 1, 2026
SMTP 441 is not a standard reply code. It usually means enhanced status 4.4.1 ("No answer from host"), a temporary failure where your server could not reach the recipient mail host, or AuthSMTP's provider-specific 441 meaning your account is over its data quota. Both are temporary: retry, or check connectivity and quota.
Retry; if it persists, check the recipient MX reachability and your outbound port 25.
What it means
RFC 5321 defines no 441 reply code. Its transient codes are 421, 450, 451, 452, 455, and a few auth codes. So "441" is almost always one of two things wearing the same label: the enhanced status 4.4.1 ("No answer from host") with the dot dropped, which is the common case, or AuthSMTP's own 441 for an over-quota account. Identifying which one you have is the whole job, so read the raw log line.
Common causes
Your server tried to open an SMTP connection to the recipient mail host and got no response, because the remote system was busy or could not take the call. This is a connectivity problem in the network and routing class, not a rejection of your content.
If you relay through AuthSMTP, 441 means the account is at or over its data quota. Each plan has a monthly allowance, and a 1 MB attachment can use 1 to 1.5 MB of quota.
How to fix it
- For 4.4.1, wait; it is transient
Most 4.4.1 deferrals clear within minutes to a few hours as the recipient host recovers. Your queue retries automatically.
- Confirm the recipient MX is reachable
Run a MX lookup, then test the connection to the MX host on port 25. No banner means the remote side is down or filtering you.
dig MX recipientdomain.com openssl s_client -starttls smtp -connect <mx-host>:25 - Check that outbound port 25 is not blocked
Many residential and cloud networks block outbound 25, which produces "no answer from host" symptoms. Relay through a smarthost or submission service instead of delivering direct to MX.
- Verify your sending IP is not silently dropped
Some receivers tarpit or refuse IPs with poor reputation. Check blocklists and confirm forward and reverse DNS match.
- For the AuthSMTP quota version
Upgrade your allowance in the AuthSMTP control panel or wait for the monthly reset, and reduce payload by linking to large attachments instead of embedding them.
Paired code
A real bounce often shows both a 3-digit code and an enhanced code together. This one commonly pairs with:
Common questions
Is 441 a real SMTP reply code?
No. RFC 5321 defines no 441. It is usually the enhanced status 4.4.1 with the dot stripped, or a provider-specific code such as AuthSMTP over-quota.
What is the difference between 441 and 4.4.1?
They are the same thing. 441 is 4.4.1 with the dot removed by logging or tooling.
How do I fix a 4.4.1 deferred error?
Usually wait; it clears on retry. If it persists, confirm the recipient MX is reachable and that your outbound port 25 is not blocked.