POP3 and IMAP are two different protocols used to access email. POP3 and IMAP function very differently from each other and each have their own advantages. POP3 is primarily used if you check your email from one single computer at a single location and have no need to access mail from multiple locations, and don’t need access to your entire mailbox from webmail. IMAP is the better option when you need to check your e-mail from multiple computers at different locations such as at work, home, or on the road, or when you use a mobile device to access email.
POP3 works by accessing the mail server and downloading all new messages to your computer, and leaves your computer entirely responsible for handling your mail from that point forward.
IMAP, the mail is stored on the mail server rather than your computer. Unless you copy a message to a “Local Folder” the messages aren’t always copied to your PC. Using this protocol, all your mail stays on the server, along with message flags (read/unread/replied), and mail can be sorted into folders on the server. This allows you to access the same mailbox from multiple computers, mobile devices or even webmail and your entire mailbox is exactly as you left it. No more trying to remember if you replied to that important client from home last night, you’ll see the “Replied” icon and you can even look in your Sent folder to see mail you sent from another computer.
With IMAP, all of your mail is protected on the server, so even if your laptop gets stolen or your hard drive dies, all of your mail is waiting for you just like nothing ever happened.
It is important to point out that POP3 can be set to leave your e-mail on the server instead of downloading to your computer. This feature enables you to check your e-mail from multiple locations just like IMAP. So why choose IMAP rather than POP3 with the leave mail on server setting? With the POP3 leave mail on server setting only your e-mail messages are on the server, but with IMAP your e-mail folders are also on the server.