Cannot enable remote SMTP server on Plesk

[jominj]

Some times we may face a situation where, cannot enable remote Mail server in Tools and Settings->External SMTP Server, the following error appears:
Error: sh: 1: /opt/psa/admin/bin/msmtpmng: not found

This error is because of MSMTP relay is not installed on the server.
Uninstall the Panel mail server and install the SMTP client: In Tools & Settings > Updates and Upgrades > Add/Remove Components > Mail hosting features select MSMTP relay only mail server (SMTP client) instead of the selected mail server.

Install MSMTP relay using autoinstaller:

Code: [Select]

# /opt/psa/admin/sbin/autoinstaller
    .....................
    Primary components list / mail
    ===============================================================================

    Select the components you want to install:

      Different mailservers
     6. ( ) Postfix mailserver
     7. ( ) Qmail mailserver
     8. (*) MSMTP relay only mailserver (SMTP client)