POP vs IMAP

2009 April 22
by Andy

I get asked this a lot – what is the difference between POP and IMAP, and why would I want one over the other?

To put it simply, IMAP stores email on your mail server, POP stores email on your local email client.

IMAP is better for a TON of reasons.

POP or Post Office Protocol, is the most common protocol to get mail from a server to a client.  The protocol has been around forever and is in use by just about all email providers.  IMAP or Internet Message Access Protocol is newer and was designed to plug the gaps left by POP.

POP was designed to work in “offline” mode, meaning that a client would connect to a mail server, download new messags and disconnect.  The messages would then be removed from the server.  This works very well if you connect to your mail server from the same computer all the time, but if you have multiple computers and or mobile devices, POP just doesn’t work well.  Messages once downloaded to one client be it computer or mobile device are then no longer available for download to another device.  There are options to leave messages on the server, but since POP does not have the ability to add state to a message (read, unread etc) leaving the messages on the server is messy.

IMAP was designed to take advantage of the mail’s state in the inbox and to be able to work in “online” mode meaning that the connection between the mail client and the server can be interactive.  Since IMAP can remember the state of a message, I can mark a mail as read on one device and have that information picked up by a different device later on.  It can also sync folders between mail client and mail server.  If you file messages to folders, IMAP will pick up this state change and synchronize between client and server.  This means that when you file a mail on your iPhone, for example, when you go home and look at your mail the filed message will be right where you expect it to be – in the folder in which it was filed.

While POP was great in the early stages of email adoption, IMAP is a more functional way to retrieve your mail.  If you can mange it, use IMAP instead of POP, you will be much happier.

Some resources for you:

http://www.imap.org/papers/imap.vs.pop.brief.html

http://www.imap.org/papers/biblio.html

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