IMAP and POP are the protocols that are used when streaming email data from a mail server, and most email clients (such as Outlook, Thunderbird, Windows Mail) will accept either when configuring email accounts. VentraIP products support the use of either protocol.
What you decide to use is ultimately up to you – one may be better than the other for your circumstances.
IMAP (Internet Message Access Protocol)
When you receive a message, the mail app will leave the message on the mail server and stream a copy to your devices. The email remains on the server, and you can access it via another IMAP mail client and view your mail exactly as it appears in your other devices, which will keep everything in sync.
POP (Post Office Protocol)
All of your emails will be downloaded to the device you access it from (into the mail client) and removed from the mail server. This will allow you to read your emails while online or offline. This is a great option if you do not wish to invest in more Disk Space or email storage as part of your plan.