Emails are sent with a wrong hostname in a sender address from a Plesk for Linux server with Postfix

Symptoms

After changing a server hostname in Plesk at Tools & Settings > Server Settings, emails are sent with an old hostname in a sender address.

Cause

The directive myhostname is explicitly defined in the Postfix configuration file /etc/postfix/main.cf:

# grep “myhostname =” /etc/postfix/main.cf
myhostname = server.example.com

Configuration defined in /etc/postfix/main.cf overwrites server-wide configuration. By default, the myhostname directive is disabled (commented with # at the beginning of the line) in /etc/postfix/main.cf.

Resolution

1. Connect to the Plesk server via SSH.

2. Open the file /etc/postfix/main.cf in a text editor. In this example, we are using the vi editor:

   # vi /etc/postfix/main.cf

3. Find the myhostname line and apply one of the following steps:

   • comment it out by placing a # (hash) character ay the beginning of the line:

     # myhostname = localhost.localdomain

   • specify a fully qualified domain name (FQDN) that will be used as a sender address:

     myhostname = server.example.com

4. Save the changes and close the file.

5. Verify the changes with the command:

   # grep “myhostname =” /etc/postfix/main.cf

6. If the file /etc/mailname exists, make sure a correct server hostname is defined in it:

   # cat /etc/mailname
   server.example.com

7. Send an email and check sender address name.