Execution of plesk repair mail utility fails: mailsrv_conf_init… not found

Symptoms

• When repairing mail with plesk repair mail, the operation fails with:

  # plesk repair mail
  Reconfiguring all domains and mailboxes ......................... [2017-09-03 11:17:31] ERR [util_exec] proc_close() failed ['/opt/psa/admin/bin/mchk'] with exit code [1]
  [FAILED]
  - mchk failed: ==> Checking for: mailsrv_conf_init... not found,
  skipped

• Symbolic link /usr/bin/which points not to /bin/which

  # ls -al /usr/bin/which
  lrwxrwxrwx 1 root root 63 Aug 24 04:04 /usr/bin/which -> ../local/share/.config/yarn/global/node_modules/which/bin/which

• Mail authorization database is empty:

  # /usr/local/psa/admin/bin/mail_auth_dump
  Authentication database contents:
  +--------------------------------------+-----+--------------------------------------+
  | address |flags| password |
  +--------------------------------------+-----+--------------------------------------+
  +--------------------------------------+-----+--------------------------------------+

• In /var/log/maillog there are records like:

  Sep 3 06:59:30 mail plesk_saslauthd[25101]: failed mail authenticatication attempt for user 'example' (password len=9)
  Sep 3 06:59:30 mail postfix/smtpd[25099]: warning: unknown[xxx.xxx.xxx.xxx]: SASL LOGIN authentication failed: authentication failure

Cause

Incorrect location of /usr/bin/which.

Resolution

1. Connect to the server via SSH

2. Change location of /usr/bin/which

   # unlink /usr/bin/which
   # ln -s /bin/which /usr/bin/which
   # ls -al /usr/bin/which
   lrwxrwxrwx 1 root root 10 Sep 4 04:15 /usr/bin/which -> /bin/which

3. If the issue persists, reinstall which package:

   # rpm -e --nodeps --noscripts which
   # yum install which -y

4. Run plesk repair mail again.