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SMTPS connection from Outlook to Plesk for Linux server does not work: SASL authentication failure: realm changed: authentication aborted

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Taras Ermoshin
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Plesk for Linux kb: technical ABT: Group B

Applicable to:

  • Plesk for Linux

Symptoms

  • On a Plesk for Linux server, Postfix is used as a mail server.
  • SMTPS connection from Outlook to the Plesk server fails to be established.
  • The following errors are found in the file /var/log/maillog:

    CONFIG_TEXT: SSL_accept error from unknown[203.0.113.2]: lost connection
    lost connection after CONNECT from unknown[203.0.113.2]
    plesk postfix/smtpd[6814]: warning: SASL authentication failure: realm changed: authentication aborted
    plesk postfix/smtpd[6814]: warning: 203.0.113.2.example.com[203.0.113.2]: SASL DIGEST-MD5 authentication failed: authentication failure

  • Plaintext authorization is disabled in Postfix:

    # cat /etc/postfix/main.cf | grep "smtpd_sasl_security_options"
    smtpd_sasl_security_options = noplaintext

Cause

Outlook is not compatible with CRAM-MD5 authentication mechanism.

Resolution

  1. Connect to the server using SSH.
  2. Open the file /etc/postfix/main.cf for editing.
  3. Comment out the following line by putting "#" at its beginning and save the changes:

    CONFIG_TEXT: #smtpd_sasl_security_options = noplaintext

  4. Restart postfix to apply configuration changes:

    # service postfix restart

Comments

4 comments

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  • Avatar
    Miha Gregorš

    Hi,

    I get this type of error in logs from other smtp/mail servers that cannot communicate with our Plesk mail server.

    SSL_accept error from unknown[203.0.113.2]: lost connection
    lost connection after CONNECT from unknown[203.0.113.2]

    I there any handshake problem?

    I have grep 'smtpd_tls_mandatory_protocols' /etc/postfix/main.cf
    smtpd_tls_mandatory_protocols = TLSv1 TLSv1.1 TLSv1.2

    Regards, Miha

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  • Avatar
    Ivan Postnikov

    Hello @Miha, please, try the solution from this article.

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  • Avatar
    Miha Gregorš

    Hi,

    thx, I will try to reinastall ca-certificates. Is plesk repair mail needed?

    Regards, Miha

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  • Avatar
    Ivan Postnikov

    @Miha

    Yes, it is required to repair mail server configuration. 

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