Step 1: Go to Tools&Settings and click Server Components. Find the “Mail Server” section and click Remote SmarterMail Server (not configured).
Step 2: Type in the necessary information about the remote SmarterMail server – its hostname, port, and administrator login and password. The hostname must resolve correctly, and the port must be accessible from the Plesk server (you must make the necessary changes to the firewall settings manually).
Step 3: (Optional) For additional security, you can enable the following options:
A.) Use HTTPS protocol allows only secure connections to the remote SmarterMail server.
B.) Check SSL certificate when HTTPS protocol is used forces the mail server certificate validity check.
Step 4: Note that to use these options, you must manually configure the remote SmarterMail server to use HTTPS following the instructions here and here.
Step 5: Click Ok. If a connection to the remote SmarterMail server could be established, it will appear in the list of available mail servers.
Step 6: To complete the mail server change, click Mail Server, select the “Remote SmarterMail Server” option from the list, and click Ok.
Step 7: To ensure that the DNS records of hosted domains point to the remote SmarterMail server, update the MX records in Plesk DNS template accordingly, following the instructions found here.
Step 8: (Optional) To enable your customers to access the SmarterMail webmail from Plesk, click Mail Server, select Remote SmarterMail Web Client under “Webmail”, type or paste the SmarterMail webmail URL into the Login page URL field, and click Ok.