When you are upgrading / Migrating your Email Servers, Often people want to set the default / Unencrypted ports to be working after Migration. Because if you change the default ports to encrypted that will be 995 and 587, You will have to reconfigure the outlook for every user and that will be the biggest fuss. So for the time being People wants to set the ports which were being used earlier. that was 110 and 25 for outlook connectivity. In this guide have shown all the steps with all the screenshot to make this happen and Note this thing I have just illustrate the POP3 in this guide but you can do the same steps for the IMAP4. 

IMAP uses port 143, but SSL/TLS encrypted IMAP uses port 993.POP uses port 110, but SSL/TLS encrypted POP uses port 995.SMTP uses port 25, but SSL/TLS encrypted SMTP uses port 465.