Postfix: Host or domain name not found Email / SMTP Origin: Network Last updated 4 Nov 2026

Postfix: status=deferred (Host or domain name not found. Name service error for name=example.com type=A: Host not found, try again)

Postfix could not resolve the destination domain through DNS — the resolver is down or unreachable, or the domain does not exist.

Exact message you may see Host or domain name not found. Name service error for name= type=Name service error for name=example.com type=MX: Host not found, try againstatus=deferred (Host or domain name not foundHost not found, try again postfixTemporary lookup failure
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Seen on: SMTP Linux

Meaning

"try again" means a temporary DNS failure (SERVFAIL, timeout); the message stays queued. Check /etc/resolv.conf and whether the server can reach its resolver. In chroot setups Postfix uses its own copy of resolv.conf under /var/spool/postfix/etc. Also confirm the recipient domain exists.

Common causes

  • Resolver unreachable or misconfigured in /etc/resolv.conf
  • Postfix chroot using a stale resolv.conf copy
  • Firewall blocking UDP/TCP 53
  • Recipient domain typo or expired
  • DNSSEC or upstream resolver errors

⚡ Quick fix

  1. Test resolution from the server: dig MX example.com
  2. Update /etc/resolv.conf, then postfix stop && postfix start (copies into chroot)
  3. Verify the domain spelling

Detailed fix by platform

Linux

  1. dig +short MX example.com; after fixing resolv.conf: cp /etc/resolv.conf /var/spool/postfix/etc/resolv.conf && postfix reload

How to diagnose

  1. DNS — dig works on the server?
  2. Chroot — Postfix copy updated?
  3. Domain — Exists?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Network. Errors that are often confused with or caused by this one (click to open):

550 5.7.25 PTR record required — SMTP: 550-5.7.25 The IP address sending this message does not have a PTR record setup, or the corresponding forward DNS entry does not point to the sending IP (Email / SMTP)550 5.7.25 PTR record…DKIM: no key for signature — DKIM: dkim=permerror (no key for signature) / key not found in DNS selector._domainkey (Email / SMTP)DKIM: no key for sign…DMARC: no record found — DMARC: dmarc=none (no DMARC record found for example.com) — bulk sender requirements not met (Email / SMTP)DMARC: no record foundHelo command rejected: need fully-qualified hostname — SMTP: 504 5.5.2 <localhost>: Helo command rejected: need fully-qualified hostname (Email / SMTP)Helo command rejected…No MX record / Domain not found — SMTP: 550 5.1.2 Domain not found / 554 5.4.4 Unable to resolve MX / Host or domain name not found (Email / SMTP)No MX record / Domain…Outbound port 25 blocked — SMTP: telnet smtp.example.com 25 — Connection timed out (cloud provider blocks port 25) (Email / SMTP)Outbound port 25 bloc…Postfix: bind 0.0.0.0 port 25: Address already in use — Postfix: fatal: bind 0.0.0.0 port 25: Address already in use (Email / SMTP)Postfix: bind 0.0.0.0…Postfix: SASL authentication failed — Postfix: warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory (Email / SMTP)Postfix: SASL authent…Postfix: …

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