While configuring outlook you will get 2 options in incoming mail server. i.e., POP3 and IMAP.
POP3 (Post Office Protocol) is an application-layer protocol used by local e-mail clients to retrieve e-mail from a remote mail server. It is a standard protocol for receiving an e-mail. Port number for POP3 is 110.
POP3 downloads copies of your email messages from a server to a single computer. Any changes you make will not be visible to other users or computers accessing the email account since you are only making changes to the local copies. You can delete the mails from server while downloading mails to reduce the disk size of the server or you can also keep a copy of mails in server.
Users can use only one computer to check mails
Mails will be stored on local computer and not in the server.
Users can keep a backup of all their messages.
No internet is required to check mails and users can read emails through offline.
IMAP (Internet Message Access Protocol) is an Internet standard protocol used by e-mail clients to retrieve e-mail messages from a mail server. It is a standard email protocol for receiving mails that stores email messages on a mail server. Port number for IMAP is 143.
IMAP allows you to read emails as they appear on the hosting server. All messages and any changes you make are seen by anyone else who logs into webmail or IMAP. IMAP requires internet access to check mails. You can configure IMAP in multiple devices for the same email address.
Users can use multiple computers and devices to check their mails.
All the mails are stored in server and not local computer.
Internet access is required to check mails.
Multiple users can access the same email account.