Solution Server error ‘550 5.1.1’ in Plesk

I got a bounce back email whose content is below and after researching, the solution is here.

Symptom:

• Domain example.com hosting di server Plesk.
• Email example.com hosting di luar server Plesk.
• Send messages via Plesk server got message : Server error: ‘550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in virtual mailbox table’

Cause:

• The email server treats example.com as a local domain and sends emails locally.

Solution:

• Enter Plesk.
• Select Domains > example.com > Mail Settings > Uncheck Activate mail service on domain and click OK.

Note : Plesk Obsidian Web Host Edition Version 18.0.23 Update #2

Please try again and good luck.