Steps to reproduce the issue

Attached is an image of the settings used.

Expected result

Mail should be correctly sent.

Actual result

The problem is that the self.defined certificate is not accepted and no mails are sent as a result.

System information (as much as possible)

PHP Built On Linux srv125.tophost.ch 3.10.0-714.10.2.lve1.4.79.el7.x86_64 #1 SMP Thu Jan 4 13:30:50 EST 2018 x86_64
Database Type mysql
Database Version 10.1.35-MariaDB
Database Collation utf8_general_ci
Database Connection Collation utf8mb4_general_ci
PHP Version 7.1.21
Web Server LiteSpeed
WebServer to PHP Interface litespeed
Joomla! Version Joomla! 3.8.12 Stable [ Amani ] 28-August-2018 14:00 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT

Additional comments

The managers of the remote email server have come up with the following solution, which unfortunately got overridden with the latest release:

/public_html/libraries/vendor/phpmailer/phpmailer/class.phpmailer.php

            x             Alteration on Linie 275 (which may have altered)

                          

                           public $SMTPOptions = array(

                                           'ssl' => array(

                                          'verify_peer' => false,

                                          'verify_peer_name' => false,

                                          'allow_self_signed' => true

                                           )

                           );

I pass this on as information.