Difference Between POP3, IMAP, and Exchange Emails

POP3 (Post Office Protocol)

POP, or Post Office Protocol, is a way of retrieving email information that dates back to a very different Internet than we use today. Computers only had limited, low bandwidth access to remote computers, so engineers created POP in an effort to create a dead simple way to download copies of emails for offline reading, then remove those mails from the remote server. The first version of POP was created in 1984, with the POP2 revision created in early 1985.

POP3 is the current version of this particular style of email protocol, and still remains one of the most popular. Since POP3 creates local copies of emails and deletes the originals from the server, the emails are tied to that specific machine, and cannot be accessed via any webmail or any separate client on other computers. At least, not without doing a lot of email forwarding or porting around mailbox files.

While POP3 is based on an older model of offline email, there’s no reason to call it obsolete technology, as it does have its uses. POP4 has been proposed, and may be developed one day, although there’s not been much progress in several years.

IMAP (Internet Message Access Protocol)

IMAP was created in 1986, but seems to suit the modern day world of omnipresent, always-on Internet connectivity quite well. The idea was keep users from having to be tied to a single email client, giving them the ability to read their emails as if they were “in the cloud.”

Compared to POP3, IMAP allows users to log into many different email clients or webmail interfaces and view the same emails, because the emails are kept on remote email servers until the user deletes them. In a world where we now check our email on web interfaces, email clients, and on mobile phones, IMAP has become extremely popular. It isn’t without its problems, though.

Because IMAP stores emails on a remote mail server, you’ll have a limited mailbox size depending on the settings provided by the email service. If you have huge numbers of emails you want to keep, you could run into problems sending and receiving mail when your box is full. Some users sidestep this problem by making local archived copies of emails using their email client, and then deleting them from the remote server.

Microsoft Exchange, MAPI, and Exchange ActiveSync

Microsoft began developing MAPI (sometimes called Messaging API) not long after IMAP and POP were first developed, although it has uses beyond simple email. Thoroughly comparing IMAP and POP to MAPI is pretty technical, and out of scope for many readers of this article. Simply put, MAPI is a way for applications and email clients to communicate with Microsoft Exchange servers, and is capable of IMAP style syncing of emails, contacts, calendars, and other features, all tied into local email clients or applications. This function of syncing emails is branded by Microsoft as “Exchange ActiveSync.” Depending on what device, phone, or client you use, this same technology might be called any of the three Microsoft products (Microsoft Exchange, MAPI, or Exchange ActiveSync), but will offer the same cloud-based email syncing as IMAP.

Because Exchange and MAPI are Microsoft products, only companies that own their own Exchange mail servers or use Windows Live Hotmail will be able to use Exchange. Many clients, including the default Android mail client and iPhone, are Exchange ActiveSync capable, giving Hotmail users IMAP style cloud-based email, despite Hotmail not offering true IMAP functionality.

Via: HTG