The main difference between POP3 and IMAP lies in how email clients (email reading programs) handle messages on the server.
Using the POP3 (Post Office Protocol) protocol, all emails are downloaded from the server to the location where the mailbox is configured (e.g., computer or phone). Nowadays, most programs using POP3 allow you to set an option to leave a copy of the message on the server. In Outlook, the default is to keep emails on the server for 14 days.
With the IMAP (Internet Mail Access Protocol) protocol, both received and sent emails are stored simultaneously on the server and in the email client. Using this protocol also enables nightly backups of the emails, making it a safer choice in case your computer breaks down.
