Resolved Proplems with closing SMTP port 25

[Martin73]

I have tried to harden my mail settings and did following things:

I have set in /usr/share/postfix/main.cf
smtpd_tls_auth_only = yes

This is the error log from Roundcube:

[08-Mar-2018 08:14:51 UTC] ERROR: SMTP server does not support authentication ()
[08-Mar-2018 08:14:51 +0000]: <206vkuds> SMTP Error: Authentication failure: SMTP server does not support authentication (Code: ) in /usr/share/psa-roundcube/program/lib/Roundcube/rcube.php on line 1648 (POST /?_task=mail&_unlock=loading1520496890784&_lang=de_DE&_framed=1&_action=send)

Then I removed the setting smtpd_tls_auth_only = yes and changed the file /usr/share/psa-roundcube/config/defaults.inc.php to:

// SMTP server host (for sending mails).
// To use SSL/TLS connection, enter hostname with prefix ssl:// or tls://
//$config['smtp_server'] = 'localhost';
$config['smtp_server'] = 'tls://localhost';

// SMTP port (default is 25; use 587 for STARTTLS or 465 for the
// deprecated SSL over SMTP (aka SMTPS))
//$config['smtp_port'] = 25;
$config['smtp_port'] = 587;

It was not possible the send an email with Roundcube. What do I have to do? I will only use port 587 or 465. Thank you in advance.

 

[Martin73]

I have changed again the setting in /etc/postfix/master.cf (the path in my first posting is wrong).

smtp_use_tls = yes
smtpd_tls_auth_only = yes

The test with my email client was successful.

After this step I changed the file /usr/share/psa-roundcube/config/defaults.inc.php to:

// SMTP server host (for sending mails).
// To use SSL/TLS connection, enter hostname with prefix ssl:// or tls://
//$config['smtp_server'] = 'localhost';
$config['smtp_server'] = 'tls://mail.example.com';

// SMTP port (default is 25; use 587 for STARTTLS or 465 for the
// deprecated SSL over SMTP (aka SMTPS))
//$config['smtp_port'] = 25;
$config['smtp_port'] = 587;

This part is important:

$config['smtp_server'] = 'tls://mail.example.com';

The entry must be for the correct mailserver. Now it's possible to check the certificate. The test with Roundcube was also successful. Everything works.