Auto-reply does not work, when SMTP email relay service provider does not accept emails from postmaster@localhost

Symptoms

Auto-reply does not work for email accounts. The following error message appears in MailEnable logfile:

PLESK_INFO: 504 5.5.2 postmaster@localhost: Sender address rejected: need fully-qualified address 32 89 postmaster@localhost Re: Email message
SMTP-OU 2346778F969647F6AFFF84D4EB584B05.MAI 2040 203.0.113.2 QUIT QUIT 221 2.0.0 Bye 6 15 postmaster@localhost Re: Email message

Cause

SMTP email relay service provider does not accept emails from postmaster@localhost.

Resolution

Change the mail account that will be used as a sender name:

1. In Plesk, go to Tools & Settings > External SMTP Server and uncheck the option Use the mail server installed with Plesk and the default mail account created by Plesk.

2. In the appeared fields, specify a valid mail account that will be used as a sender name. Once done, click OK.