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POP and IMAP are two ways an email client can fetch your email.

When I send you an email, I’m not sending it right to your computer. I’m sending it to gmail.com, or yahoo.com, or hotmail.com or some other mail server out on the Internet. POP and IMAP are two ways your computer can fetch your mail from that mail server.

POP stands for Post Office Protocol, and you can think of it as working like a post office. When you go to the post office to pick up your mail, the post office doesn’t save a copy. Same with POP. When you fire up Outlook and it fetches all of your mail from the server, it deletes it from the server and stores it on your computer.

IMAP, on the other hand, stands for Internet Messaging Access Protocol and is like if the post office kept a copy of your mail. It marks the ones you’ve read and replied to, but doesn’t delete them from the server unless you tell them to.

IMAP is great if you need to access your mail from multiple computers. Even if you’ve read your messages from home, they’ll still be there if you check your mail from work. If you were using POP, it’d be a mess – you’d have some emails stored on your computer at home, and others stored on your computer at work. When you hear about storing your email “in the cloud,” that’s IMAP.

Sometimes there’s an option with POP to leave your mail on the server. There’s a catch, though – since you can’t mark messages as read on the server with POP, every time you check your mail on a new computer it thinks all of your mail is new. That’d be like stopping by a post office and having them hand you copies of all the mail you’ve ever gotten, all at once!

POP used to be the most common protocol for accessing email, but IMAP has become more and more popular. This is thanks to both consumer demands and advances in technology – we’re likely to check our mail from many devices, making POP impractical. So next time Outlook or Mail.app asks you if you want IMAP or POP, you’ll have all your ducks in a row.

Cocktail Party Fact

While the first telephone call will live on forever – Alexander Graham Bell’s “Mr. Watson, come here I want you.” – email’s birth is not nearly so memorable. The first email was a test sent by Ray Tomlinson, who says it was something like “QWERTYUIOP”. Not one for the history books!