Comparison POP, IMAP and Exchange.

Here is a pretty comprehensive comparison between POP, IMAP and Exchange.

POP

* Not made for keeping multiple computers/devices and web in sync
* Generally, mail is downloaded from the server upon checking it (unless you use a tool like Outlook which has the ability to leave it on the server)
* Even if you leave messages on the server, if you delete on remote device, it will not delete on the server (unless you have a client tool like Outlook which will give you some options)
* If you send from remote device, it is not pushed to a sent items folders on the server
* Only brings messages down in the Inbox (not sub-folders)
* No good push capability for mobile devices (as of this writing)
* POP is low cost
* Most personal email accounts use POP (i.e. Gmail)

IMAP
* Keeps multiple computers/devices and web in sync
* Mail is left on the server when checked
* Inbox and sub-folders are brought down to client machine/device
* Push mail available on mobile devices, but many complain of poor support
* Newer than POP
* Catching on among personal users who do not have Exchange

EXCHANGE
* The most robust email platform
* Mail is kept on the server
* Allows calendar, tasks, notes, etc. in addition to email
* Allows group collaboration of calendars, etc. when used in a group environment
* Excellent about keeping everything (PCs/mobile devices/web) in sync
* Push email for mobile devices (Blackberry and non-Blackberry with Exchange ActiveSync)
* Pretty much the standard for medium size and enterprise email/collaboration
* High initial investment in hardware, need a Exchange specialist to maintain it, but affordable when it's hosted with SyncMyMail.
* Gaining popularity among small businesses and personal users as it becomes more affordable