Unable to start Postfix in Plesk: /usr/sbin/postconf: libmysqlclient.so.18: cannot open shared object file: No such file or directory

Symptoms

• On a RHEL-based Linux server, domain creation in Plesk fails with an error that is similar to the following:

  Nothing of nonexisting mail features are not supported

• Postfix cannot start due to an error that is similar to the following:

  /usr/sbin/postconf: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory

• The plesk repair mail command execution ends with an error that is similar to the following:

  # plesk repair mail
  Repairing the mail server configuration
  Reconfigure all domains and mailboxes? [Y/n]
  Reconfiguring all domains and mailboxes .........................
  ERR [util_exec] proc_close() failed
  ['/usr/local/psa/admin/bin/mchk'] with exit code [1]
  [FAILED]
  - mchk failed: ==> Checking for: mailsrv_conf_init... fail
  Error messages: 0; Warnings: 0; Errors resolved: 0
  exit status 1

• The postfix check command shows the following error:

  # postfix check
  postfix: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory

• The libmysqlclient.so.18 package cannot be found:

  # rpm -qf /usr/lib64/mysql/libmysqlclient.so.18
  error: file /usr/lib64/mysql/libmysqlclient.so.18: No such file or directory

Cause

The libmysqlclient.so.18 package is missing on the server (which can sometimes happen due to a MySQL/MariaDB version upgrade).

Resolution

1. Connect to the server via SSH

2. Install the missing package manually:

# yum install mysqlclient18-compat --enablerepo=mysqclient

3. Update the package version for Plesk:

# plesk sbin packagemng -sdf