4.4.1 SMTP bounce: no answer from host

What 4.4.1 means

The outbound connection attempt was not answered, usually because the remote system is busy or unreachable. Transient; retry later.

Message text

No answer from host

Common causes of 4.4.1

• Receiving host did not answer the connection
• Receiving host is busy or down

How to fix 4.4.1

1. Retry later; the queue does this automatically.
2. Run MX lookup to confirm the recipient domain's MX hosts exist.

Check your domain

Check the MX records of the recipient domainRuns in your browser; nothing is uploaded.

Have the full bounce message? Paste it into the bounce code lookup and it will match the code and the provider for you. Open the bounce code lookup.

How to read 4.4.1

The second part, 4.4.1, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 4 is a Persistent transient failure (4xx): the command was not accepted, but the condition may clear, so the sender should try again later (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 4 is network and routing: a problem reaching or routing to the destination. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.

Sending servers should retry a deferred message. RFC 5321 §4.5.4.1 advises waiting at least 30 minutes between attempts and trying for at least 4 to 5 days before giving up and returning a bounce. If the deferral keeps repeating, fix the cause rather than waiting.

Official source: www.rfc-editor.org. Last verified 2026-10-20.

Related guides

• How to create an SPF record (syntax and examples)
• How DKIM works and how to publish a DKIM record
• How to set up a DMARC record, from p=none to p=reject

Related codes

• 421 SMTP: service not available
• 450 SMTP: mailbox unavailable
• 451 SMTP: local processing error
• 452 SMTP: insufficient storage
• 4.2.2 SMTP: mailbox full
• 4.7.0 SMTP: security status

FAQ

All bounce codes