IMAP and POP are two different protocols. There are many differences between these two. The main difference is that IMAP(Internet Messaged Access Protocol) always syncs with the mail server so that any changes you make in your email client (Microsoft Outlook) will instantly appear on all computers that have that same account configured in their outlook. Basically all Microsoft outlooks will have the same exact information, this includes all sent emails, inbox emails, replies, and contacts.
On the other hand, in POP(Post Office Protocol), your email client (Microsoft Outlook) will not sync with all computers that have the email account configured in their Microsoft Outlook. It means whatever changes you make to your email account in the mail client will not be synced or show up in the other computers that have that account configured.
In simple terms, if you are using IMAP and mark a mail as read, it gets marked as read in all the devices or computers that have that account configured. However, this won’t be the case if you are using POP, because the mails are downloaded to your PC and the changes made there stay there. It won’t reflect on the other computers or devices. If you reply to an email using the POP option then only your computer will see that reply, the other computers will not see that the message was replied to.
