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

Symptoms

• Plesk service messages (notifications, auto-replies, password reset links) are not sent be the server

• A similar error is displayed on attempt to send a message with password reset link:

  PLESK_ERROR: Error: Unable to send the secret code: Your domain does not seem to be valid. Could not find MX record for your domain.

• Similar errors can be found in %plesk_dir%\Mail Servers\Mail Enable\Logging\SMTP\SMTP-Activity-<date>.log:

  CONFIG_TEXT:  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

  OR

  CONFIG_TEXT: SMTP-IN 93F3B59DDD35483EEDC8435AE43CC961.MAI 1044 127.0.0.1 MAIL MAIL FROM: noreply@example.com 501 Your domain does not seem to be valid. Could not find MX record for your domain. 86 52 postmaster@localhost

  OR

  CONFIG_TEXT: SMTP error from remote mail server after MAIL FROM:<postmaster@localhost>: 550 5.1.0 MXIN401 Your Mailfrom Domain localhost is blacklisted here

• For external/local SmarterMail server, the following error can be found at C:\SmarterMail\Logs\YYYY.MM.DD-delivery log :

  CONFIG_TEXT: 504 5.5.2 postmaster@localhost: Sender address rejected: need fully-qualified address

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.