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Unable to send an email from Plesk server: SMTP Error (535): Authentication failed

Sergey Senko
Updated
Plesk for Linux kb: technical ABT: Group A mail

Applicable to:

  • Plesk for Linux

Symptoms

  • While trying to send an email via Roundcube, the following error appears:

    SMTP Error (535): Authentication failed

  • compatibility_level value was previously defined in /etc/postfix/main.cf as following:

    compatibility_level=2

In /var/log/maillog following entries can be found:

warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory
warning: SASL authentication failure: Password verification failed
warning: localhost[::1]: SASL PLAIN authentication failed: generic failure

Cause

The root cause is under investigation.

Resolution

  1. Login to the server via SSH.

  2. Create a backup of /etc/postfix/master.cf:

    # cp -p /etc/postfix/master.cf /etc/postfix/master.cf_bck

  3. Check SMTP daemon configuration:

    • If RHEL/CentOS/CloudLinux is used, verify that chrooted mode is disabled:

      # egrep "^smtp " /etc/postfix/master.cf | grep inet
      smtp inet n - n - - smtpd

    • If Debian/Ubuntu is used, verify that chrooted mode is enabled:

      # egrep "^smtp " /etc/postfix/master.cf | grep inet
      smtp inet n - y - - smtpd

  4. Reload postfix configuration:

    # service postfix reload

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Comments

1 comment
Date Votes
  • Avatar
    Svalon

    But how should this fix it ?

    We just check something here but change nothing.

    I have this issue and don't know how to fix it

    -1

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