Port 465 is open and listening but unable to route emails through this port

We are using MIAB from last month and it is very useful. Thank you for this service.
The problem we are having is: we have to configure outlook with MIAB but unfortunately this mail client doesn’t support STARTLS so, we thought of taking another route by opening the 465 port.

I uncommented the smtps from the master.cf and allowed the port 465 in firewall. now server is listening to port 465 but it is still not transferring the email through this port. The guide I followed is How to temporarily enable SMTPS (port 465)
but it was an old thread so I don’t know if this still effective.

Any help is appreciated. Thank you