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How to prevent plaintext authentication via IMAP/POP3 and SMTP in Postfix on Plesk server?

Aleksandar Stoev
Updated
kb: how-to Plesk for Linux ABT: Group B

Applicable to:

  • Plesk for Linux

Question

How to prevent cleartext / plaintext authentication via IMAP/POP3 and SMTP in Postfix on Plesk server?

Answer

Note: If you don't have root access to the Plesk server via SSH, contact your service provider regarding this issue.

Click on a section to expand

Plesk with Dovecot + Postfix

  1. Connect to the server via SSH

  2. Execute the following command to disable plaintext (cleartext) authentication:

    # plesk bin mailserver --allow-plaintext-auth false

 

Note: If Qmail is used, it is recommended to switch to Postfix. Forcing secure connection over SMTP in Qmail requires patching which is not supplied by Plesk.

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Comments

2 comments
Date Votes
  • Avatar
    Voelu28

    Doesnt work on Ubuntu 20.04.6 LTS with Plesk Obsidian 18.0.62 Update 2:

    # sudo service saslauthd restart && service postfix restart && service dovecot restart
    # Failed to restart saslauthd.service: Unit saslauthd.service not found.

    After i followed your tutorial no mails could be send anymore. TLS/SSL is always activated in mail client.

    I need to redo the changes.

    0
  • Avatar
    Steve Yates

    On RHEL-based, smtpd.conf is in /etc/sasl2/smtpd.conf not /usr/lib64/sasl2/smtpd.conf.

    0

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