Have a look at this chain as it's similar to what you have
I am going to assume your domain is: mail.ve3nrt.net as per your previous post
A) A gentle review of Port Numbers and how they should work
B) I can see you have port 587 and 993 open which are SMTP over SSL and IMAP over SSL
C) You should review the concept of STARTTLS as it will explain your observations below
Outlook Windows works when I use TLS on port 143, or SSL on 993, although 993 doesn’t work with TLS. I even got RPA (require password authentication) to work for the first time ever. By default, Outlook for Android tries to use 993, I found out, but forcing it to 143 by specifying the port after the fqdn of the imap server doesn’t work either, although the port it tries to connect on does indeed change
Your observations are what I would expect to see from a mail server. My testing is below
SMTP on Port 25: No SSL Handshake with No starttls
SMTP on Port 25 with STARTTLS: Handshake
IMAP on Port 143: No SSL Handshake with no STARTTLS
IMAP on Port 143: SSL Handshake with STARTTLS
SMTPS on port 587 - Handshake with STARTTLS
SMTPS on port 587 - No Handshake with no STARTTLS
IMAPS on Port 993 - handshake with no STARTTLS flag
