Firstly it is important to distinguish the difference between POP and IMAP.
POP: POP email is your conventional email account provided by other ISP's, where all your email is downloaded off the server onto your PC.
IMAP:All IMAP email is always stored on the server, but it allows you to temporarily download emails to view on any PC. When you are finished with reading your mail, the server logs you off and the mail is left on the server for next time.
Steps to Setup IMAP Email Account