Question
What does the following warning found in /var/log/maillog mean?
postfix/smtpd[10643]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
Answer
The NIS (Network Information System) allows a group of machines within an NIS domain to share a common set of configuration files. If there are email servers running on more than one box, NIS can share the configuration files between them.
This warning may be safely ignored, as it does not cause problems when there is a single server running.
Steps to remove the warning
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Connect to the server over SSH
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Run this command to get the "NIS" line from the Postfix configuration
# postconf | grep "nis:mail.aliases"
alias_maps = hash:/etc/aliases, nis:mail.aliases, hash:/var/spool/postfix/plesk/aliases -
Remove
nis:mail.aliasesfrom postfix configuration with this command# postconf -e "alias_maps = hash:/etc/aliases, hash:/var/spool/postfix/plesk/aliases"
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Restart Postfix to apply the changes
Warning: Restarting Postfix will cause downtime for mail delivery; restart during a maintenance window
# service postfix restart