Unable to send mail from Plesk: 554:5.7.0 Your message could not be sent. The user filteramm is not allowed to send email

Symptoms

• All emails that are sent from the Plesk server are rejected with the following error in /var/log/maillog:

  554:5.7.0 Your message could not be sent. The user filteramm is not allowed to send email. : Command died with status 100

• Massive Adjust Mailbox extension is installed on the server in Extensions > My Extensions menu

Cause

Critical Massive Adjust Mailbox extension is not compatible with Plesk version that is currently in use

Resolution

1.  Connect to the server via SSH
2. Run the following command to make extension compatible with Plesk version:

   # /usr/local/psa/admin/sbin/mailmng-outgoing –add-to-whitelist –sysuser=filteramm