Want to know if it's a mess or simple to set up my system to work on a different
port for SMTP than 25.
I don't want to loose my real incomming mailtraffic ofcourse ;-)

The reason why, is that my phone-ISP doesn't allow traffic from their network
on port 25 to the outside world - so I cannot use
my own sending server when sending mail from my phone.
(use IMAP as connection to read and authenticated smtp for sending)

Is there any solution.

I used to use my GMS client on the phone, but it crashed and haven't got
time to troubleshoot why it doesn't work although many reinstallations.