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Mail queue in Plesk contains deferred emails: Host or domain name not found

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Renan Poss Moreira
Updated
Plesk for Linux kb: technical ABT: Group A

Applicable to:

  • Plesk for Linux

Symptoms

  • There are deferred (unsent) emails in Plesk > Tools and Settings > Mail Server Settings > Mail Queue, that failed to be sent to @example.com address.

  • The following error is shown in /var/log/maillog :

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

  • The remote may be resolved from Plesk server:

    # dig example.com +short
    # dig example.com mx +short

  • The remote host can be resolved from a different server:

    # dig example.com +short
    203.0.112.2
    # dig example.com mx +short
    10 mail.example.com

Cause

The server is configured to use a DNS resolver that cannot be reached or cannot resolve DNS names. Alternatively, it may be possible that there are no DNS servers configured in /etc/resolv.conf.

Resolution

1. Connect to the server via SSH

2. Add proper resolver to /etc/resolv.conf. For example:

# cat /etc/resolv.conf
nameserver 8.8.8.8

3. Restart postfix:

# systemctl restart postfix

Note: If in /etc/resolv.conf there are more nameservers, please set it on top of the nameservers list. Nameservers list order matters.
Note:  Sometimes, In Debian/Ubuntu OSes  /etc/resolv.confcan be managed only by system utilities and manual adjustments may not work. In this scenario, it's necessary to do some extra steps as mentioned here

Warning: Make sure that the nameservers configured in the server are reachable from the server network

Comments

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  • Avatar
    Georgios Papadopoulos

    A solution you might try is, go to:

    Home > Tools & Settings > Server-wide mail settings > Settings

    Limitations on outgoing email messages

    The following limits are default. They can be overridden in each service plan and subscription. The limits do not work server-wide, but act as a template for the plans and subscriptions for which no custom limits were specified. Note that switching on the limitation of outgoing email messages can affect the mail server performance. Learn more about limiting outgoing mail

    Disable this: Turn on limitations on outgoing email messages

     

     

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