Both POP (Post Office Protocol) and IMAP (Internet Message access protocol) allow people to get access to their email from a remote server; however, that is where most similarities end. POP simply downloads email to your computer, and usually (but not always) deletes the email from the remote server. The problems arise if you have more than one device where you read your mail (desktop, laptop, tablet or phone). Here’s why it’s bad: You have to delete or file the same email on every device
Logging into each device, you will see lots of unread emails with no indication of which you deleted, read, flagged or filed Any folders you created and organize on one device won’t be replicated on the other devices
IMAP allows users to store their email on remote servers. This two-way protocol also allows the user to synchronize their email among multiple devices, which is extremely important today, when most people have at least two devices – their laptop and smartphone.