Outlook 2016 for Mac supports several different account types such as POP, POP3, IMAP. Some features in Outlook require a Microsoft Exchange Server account. Microsoft Office 365 includes Exchange Online and some Internet hosting providers also offer Exchange accounts.
Tip: If you are adding an account to Outlook 2016 for Mac and you don't know which type of account it is, check with your e‑mail provider, Internet service provider (ISP), or email administrator.
To find out what type of account you have, do the following:
On the Home tab, click Accounts.
In the Accounts box, in the left pane, click on an account.
At the top of the right pane, it will tell you what kind of account it is. (i.e., Exchange, IMAP, or POP)
Note: Most modern e-mail clients and servers support POP3, and it, along with IMAP are the two most prevalent Internet standard protocols for email with many web email service providers such as Gmail, Outlook.com and Yahoo! Mail - also providing support for either IMAP or POP3 to allow mail to be downloaded.