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

**Code:** `Postfix: Host or domain name not found` · **Category:** Email / SMTP · **Seen on:** SMTP, Linux

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

## 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?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/email/postfix-host-not-found-name-service-error)