IMAP creates a master copy of your email stored on the email server. Other providers – most notably ISPs – may not be so generous but then, you may not get multiple gigabytes of email a year like I do. The last four years’ worth of email in my personal account uses a little over 40% of the 25 gigabytes of storage provided by Gmail. To put it into perspective: as you might imagine, I get a fair amount of email.

If your email provider has a limit to how much email can be kept, and you get a lot of email, then IMAP may not be for you. The biggest single practical difference between IMAP and the older POP3 is that with IMAP, your email is always left on your email service provider’s server. I’ll examine IMAP, how it compares to POP3, and when you might want to consider using it. IMAP is an alternative to POP3 (Post Office Protocol 3), works in some fundamentally different ways, and makes a few fundamentally different assumptions. It’s a fancy name for a protocol used by email programs like Outlook, Thunderbird, and others to access your email.

IMAP stands for “Internet Message Access Protocol”.