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Knowledge Base

Sending messages from webmail fails: SMTP Error (250): Authentication failed

 
mailphpplesk for linuxpostfixserver

Symptoms

  • Rouncube shows error:

    SMTP Error (250): Authentication failed

  • Checking server externally with telnet is not showing the AUTH option at all to the EHLO command:

    # telnet 203.0.113.2 25
    Trying 203.0.113.2...
    Connected to 203.0.113.2.
    Escape character is '^]'.
    220 203.0.113.2
    ESMTP Postfix
    EHLO example 
    250-203.0.113.2
    250-PIPELINING
    250-SIZE 51200000
    250-ETRN
    250-STARTTLS
    250-ENHANCEDSTATUSCODES
    250-8BITMIME
    250 DSN

  • In the /var/log/plesk-roundcube/errors the following error may be shown:

    SMTP Error: Authentication failure: SMTP server does not support authentication (Code: ) in /usr/share/psa-roundcube/program/lib/Roundcube/rcube.php on line 1667 (POST /?_task=mail&_unlock=loading1554712039855&_lang=en_US&_framed=1&_action=send)

Cause

Postfix misconfiguration.

Resolution

  1. Connect to the server via SSH;

  2. Check that smtpd_tls_protocols, smtpd_tls_ciphers and smtpd_tls_security_level, smtpd_sasl_auth_enable are set as below using the following command:

    # grep -E "smtpd_tls_protocols|smtpd_tls_security_level|smtpd_tls_ciphers|smtpd_use_tls|smtpd_sasl_auth_enable" /etc/postfix/main.cf
    smtpd_use_tls = yes
    smtpd_tls_security_level = may
    smtpd_tls_ciphers = medium
    smtpd_tls_protocols = TLSv1 TLSv1.1 TLSv1.2
    smtpd_sasl_auth_enable = yes

  3. Make sure that smtpd_tls_exclude_ciphers, smtpd_sasl_security_options, smtpd_tls_auth_only and tls_ssl_options are not defined in /etc/postfix/main.cf file (the output of the command below should be empty):

    # grep -E "smtpd_tls_exclude_ciphers|smtpd_sasl_security_options|smtpd_tls_auth_only|tls_ssl_options" /etc/postfix/main.cf

  4. Reload postfix if any changes were made:

    # service postfix reload

 

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