With iPhones and Google Apps for email and desktops, laptops, and netbooks, the POP versus IMAP question keeps popping up. What is the difference?

The short answer: Use POP if you have one or two devices getting email. Use IMAP if you have 3 or more.

In theory, if you use POP from, say, Outlook, Outlook will pull the email from the server and it will be in your Outlook and no longer on your server. If you used IMAP, it would sync the two places and you’d have mail in both places, even in the same folder structure. So, POP pulls email from one place to another, IMAP syncs it and it’s in both (or many places).

In practice, however, using something like Google Apps, even using POP with Outlook, it doesn’t take it from the server. Well, you can change the settings telling it what to do, but you can choose to leave it on the server. So in that sense, it’s similar. Except that IMAP will sync folders (and labels in Google Apps) if you’d like that.

But maybe the most important part of all this has to do with the multiple devices we’re using to get email: the smart phone, the laptop, someone else’s laptop, your netbook, your desktop, etc. Depending on your email host, your desktop could check mail and pull it off the server so that if you checked that same account from your smart phone it would say that you didn’t have any new mail. This can get confusing.

Verdict? Just use IMAP. Keep mail synced for all devices. All mail is there, all folders are there, on every device, all the time. Also, if you choose one or the other, you can switch back later without too much trouble.

A quick search found these helpful links on the same topic:

One last note. A client had mail go missing from her desktop and/or her iPhone. She was using POP and we couldn’t figure out where the mail was going. Turns out, she had set up another POP account on the iPhone for the same mail account so the two accounts were battling over the email. Check other computers, old laptops, etc. to see if your mail is being pulled in from elsewhere. One sure-fire solution is to change your email password so that those old devices won’t be able to get the mail.