There are two Message Transfer Agents (MTA) that are supported by Parallels Plesk Panel since version 9, including Qmail and Postfix. Each time, only one of them is used by Parallels Plesk Panel. The MTA that is currently used by Parallels Plesk Panel is shown on the Services management page at Home -> Services Management:

  • SMTP Server (Postfix)
  • SMTP Server (QMail)

It is also possible to check the MTA using the Parallels Plesk Panel utility mailmng:

    ~# $PRODUCT_ROOT_D/admin/sbin/mailmng --features | grep SMTP_Server
    $features['SMTP_Server'] = "Postfix";
    $features['SMTP_Server_package'] = "postfix";


    ~# $PRODUCT_ROOT_D/admin/sbin/mailmng --features | grep SMTP_Server
    $features['SMTP_Server'] = "QMail";
    $features['SMTP_Server_package'] = "psa-qmail";


You can switch the MTA from Qmail to Postfix and back using an autoinstaller script.

Run the script without parameters:

    ~# /usr/local/psa/admin/sbin/autoinstaller 

and select Plesk version which is marked with (currently installed) on the fourth page. Disable all other applications like SSO and Sitebuilder.

On the main components list for Plesk page, select Qmail or Postfix mailserver and click Enter to complete the installation.

Alternatively, you may run the following command to switch MTA to Postfix:

 ~# /usr/local/psa/admin/sbin/autoinstaller --select-release-current --install-component postfix

and the following command to switch to Qmail:

 ~# /usr/local/psa/admin/sbin/autoinstaller --select-release-current --install-component qmail

Additional information

The location of the directory where email messages are stored ($PLESK_MAILNAMES_D) and the mail format is not changed when the MTA is switched.

NOTE: Old mail messages remain unchanged and they are available.

However, the mail queue is reconfigured while switching the MTA and all messages that are still in the queue are lost. Before switching, it is recommended that you stop the SMTP service to prevent accepting emails and also deliver all queued mail.

By using the following command, you may stop the SMTP service:

    ~# /usr/local/psa/admin/sbin/mailmng --stop-smtpd

To flush the queue, use the following commands:

QMail MTA:

    ~# kill -ALRM `pidof qmail-send`

Postfix MTA:

    ~# postqueue -f

Find MTA:
/usr/local/psa/admin/sbin/mailmng --features | grep SMTP_Server

Kaynak :