If your email is set to use POP, your device will download email from the server, and save it locally. By default, POP will delete mail from the server once it has been downloaded (so the emails only exist locally on your computer/tablet/phone) but it can also be configured to leave a copy on the server.
POP stands for "Post Office Protocol"
If your email is set to IMAP, your device will leave all your emails on the server, and only download them temporarily, so at the end of the day, your emails all remain on the server, where they can be accessed and re-downloaded whenever you want to check your email.
IMAP stands for "Internet Message Access Protocol"
How do I choose?
POP is the older and simpler of the two methods; it is recommended to only use POP if you only check your email from one device. If you are using POP, and you have two or more different devices that you can check your email from (for example, a laptop and a phone) anything you do on one device will not be visible on the other devices.
With POP, you can access all of your previously downloaded mail without connecting to the internet. This was more of an advantage back in the days of dial-up internet, nowadays, most of us are connected to the net all the time anyway. With IMAP, you may have to connect to the internet to view previously received emails, but often they are cached and will be available offline as well.
One significant disadvantage of POP is, because emails are saved locally, if your computer dies, you may lose all the email stored on it. With IMAP, on the other hand, mail is stored on the server. If you use IMAP and your computer dies, all you have to do is log in with a new computer, and all your emails will still be there.
IMAP, is also ideal if you want to check your email from multiple devices, and have them all in sync. For example, let's say you use IMAP and have your email set up on your computer at home, and on your phone. If you get an email while you're out and about and reply to it on your phone, when you get home and check your email on your computer, everything you did on your phone while you were out will be there: messages you read on your phone will be marked read on your computer, and any replies sent from your phone will be visible on your computer as well, and vice versa.
Choose POP if:
- You want to manage your email independently on each device, or...
- You want to access your email from only one device
- You want access to your email any time, without being connected to the internet all the time. (you'll still need to connect to send and receive)
Choose IMAP if:
- You want to access your email from multiple devices, and have them all in sync
- You want to make sure all your emails are backed up in the case of computer/tablet/phone failure
- You want to keep your options open for future expansion
If you're still uncertain, we generally recommend IMAP. It tends to be more flexible, reliable, and future-proof.