Connection of Mautic with Outlook monitored Mail Box

I have installed the open source Mautic on my Ubuntu 0.18.04.4 server. Below are the details
My Mautic version is: v2.16.0
My PHP version is: 7.2.24

My problem is: I am trying to connect monitored mailbox with outlook. But while connecting with TLS Encryption (which is suggested by outlook mailbox) it is giving me an error “Error communicating with the IMAP server: [CLOSED] IMAP connection broken (server response)”.
However I tried to connect with SSL encryption as well which was a Success, but still I wan not able to fetch folders for unsubscribe and contact replies.

These errors are showing in the log:
[2020-04-26 06:30:56] mautic.NOTICE: PHP Notice - SessionHandler::gc(): ps_files_cleanup_dir: opendir(/var/lib/php/sessions) failed: Permission denied (13) - in file /mautic/vendor/symfony/http-foundation/Session/Storage/Proxy/SessionHandlerProxy.php - at line 86 {“maxlifetime”:1440}
[2020-04-26 06:52:01] mautic.NOTICE: PHP Notice - SessionHandler::gc(): ps_files_cleanup_dir: opendir(/var/lib/php/sessions) failed: Permission denied (13) - in file /mautic/vendor/symfony/http-foundation/Session/Storage/Proxy/SessionHandlerProxy.php - at line 86 {“maxlifetime”:1440}
[2020-04-26 10:06:06] mautic.NOTICE: PHP Notice - SessionHandler::gc(): ps_files_cleanup_dir: opendir(/var/lib/php/sessions) failed: Permission denied (13) - in file /mautic/vendor/symfony/http-foundation/Session/Storage/Proxy/SessionHandlerProxy.php - at line 86 {“maxlifetime”:1440}
[2020-04-26 17:36:00] mautic.WARNING: The reference for contact 3662 and IP address 28739 is already there. (Unique constraint)

Steps I have tried to fix the problem:
I have tried connecting with the app password from outlook as well. Now I can’t think of any solution here. Please help me out, if someone knows how to fix this problem.