POP3 and IMAP are protocols for connecting email servers to email clients. Or, said in normal English, they are two different methods for allowing you to download email messages to your computer, phone or tablet. Even if you’re not a hard-hitting techie, you’ve probably heard one or both of these terms before.
In the most general sense, the end result is the same. (There are differences—we’ll get to those.) Both are reliable technologies and both will give you access to your email. In fact, both of them have been around a while. A long while. Since the 1980’s, if you can believe that.
Okay, so how are they different? To answer that question, here’s a quick explanation of why these technologies are even needed. When a new email is sent to you, it’s actually sent to a server somewhere out there in the cloud. If you want to check your email via a cloud service, like Gmail, you can do so without the help of either POP3 or IMAP. But if you want to check your email on your smart phone, or if you prefer Outlook or Thunderbird (two popular desktop email clients) over Gmail’s web interface, you need some way of connecting that remote server to your phone or computer.
The email, out there on the server, needs a way to get to your email client, whether on your phone, tablet or desktop. POP3 and IMAP are like bridges. They connect your local email client to the cloud-based servers where your email resides.
As said before, both are reliable technologies. They both get the job done, but they do it a little differently. Let’s stick with the analogy of a bridge. The POP3 bridge is strictly one-way. Email can travel over it to your email client, but then the connection to the remote server is dropped. From that point, what you do with the email on your email client has no effect on the email on the server. Delete it on your phone, for example, and it will still be there on the server. POP3 will not sync both ways, only one way.
IMAP, on the other hand, is a two-way street. Instead of just sending messages over to your email client and dropping the connection, it maintains a connection and syncs messages in both places. Delete a message on your phone, and it gets deleted on the server, as well.
Which is better? Well, that depends on how you use your email. If you don’t want your phone to sync to the cloud, POP3 is certainly the way to go. On the other hand, if you want your email synced in each location, IMAP may serve you better.
See also: Set up Gmail in Outlook 2013
I’ve used both and never had issues with either. Both have reliably delivered my email. In fact, for a while I opted for POP3 specifically because I didn’t want my work email synced across devices, and it worked like a charm. Just decide which option, synced or not synced, will work best for you, and then use the “bridge” that fits your needs.