POP3 and IMAP are two different protocols (methods) used to access email. Each has its own advantages.
POP3 downloads email from a server to a single computer, and then deletes it from the server. So POP3 is most useful if you want to keep all your email on one computer and check emails only on that computer, and not from any other device.
IMAP is the better option when you need to check your emails from multiple devices, such as a work laptop, a home computer, or a tablet, smartphone, or other mobile device. Tap into your synced (updated) account from any device with IMAP.
Microsoft Exchange This type of email account behaves much like IMAP but the server is a Microsoft Exchange server. This is mostly used by big companies.
Same as IMAP, Contactually has no problem connecting with these types of email accounts. If you are using Exchange and you want to set it up with Contactually, you will need to know your Exchange server and username. This can be your email address, everything before @ in your email add, DOMAIN\username or your username. Your IT administrator or webhost will be the best person to ask about this.