How to convert POP3 incoming mail servers into IMAP?

[Shirley He]

I have POP3 mail servers set up, but recently have been having trouble with the stability of the connection. I was notified that IMAP would be more secure.

Is changing POP3 mail server to an IMAP one as simple as just selecting IMAP from the protocol dropdown list?

[Andy Brook]

I'm not sure that will help, stability != security, from many years of experience with this, POP is usually less error prone than IMAP, but sure you can try. 

If your mailserver supports the protocol (eg gmail), yes, you can change your inbound mail source to IMAP.  Be sure to pick the right 'folder' and that mail retrieval is set on your mailserver to start from 'this point forward'.