- Plesk for Linux
Emails cannot be sent via the Rouncube webmail with the following error message:
PLESK_INFO: SMTP Error (535): Authentication failed.
Emails cannot be sent via a PHP script:
PLESK_INFO: SMTP -> ERROR: AUTH not accepted from server: 535 5.7.8 Error: authentication failed: encryption needed to use mechanism
SMTP -> FROM SERVER:250 2.0.0 Ok
Fatal error: Uncaught exception 'phpmailerException' with message 'SMTP Error: Could not authenticate.' in
When using the "telnet" utility to connect to localhost on port 25, the following error message appears (commands are shown in bold):
# telnet localhost 25
Connected to localhost.
Escape character is '^]'.
220 server.example.com ESMTP Postfix
535 5.7.8 Error: authentication failed: encryption needed to use mechanism
The following error message appears in the logfile /var/log/messages:
CONFIG_TEXT: postfix/smtpd: warning: localhost.localdomain[::1]: SASL PLAIN authentication failed: encryption needed to use mechanism
The current Postfix configuration does not allow the use of mechanisms that transmit unencrypted username and password information.
Note: If you are a domain owner, contact your service provider for assistance.
Connect to a Plesk server via SSH.
Open the file /etc/postfix/main.cf in a text editor and comment the line "smtpd_sasl_security_options" with the "#" character:
CONFIG_TEXT: #smtpd_sasl_security_options = noplaintext
# service postfix restart