Sending mail from System email with SMTP SSL, STARTTLS not working
short description
Sending mail from System email with SMTP SSL, STARTTLS not working but with Plain works. I have set in System->Interface->Main Config->Mail "Use SMTP to send system mails" setup not working except plain. When I set up SSL (port: 465) and STARTTLS (port: 587) then it does not sending email. I checked it with forgot password function. It shows success message but mail does not received. But it's working with PLAIN setting with on 25 port.
environment
Server OS: Debian
Server OS version: jessie
ISPConfig version: 3.1.15p2
Server version: Apache/2.4.10 (Debian)
Server built: Sep 30 2019 19:32:08
PHP 7.4.1 (cli) (built: Dec 18 2019 17:05:02) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
with Zend OPcache v7.4.1, Copyright (c), by Zend Technologies
log entries
/var/log/ispconfig/ispconfig.log is empty. Setting is with Error level.