Google has upped the ante when it comes to relying on Gmail as a full featured e-mail service with its introduction today of free IMAP access to your Gmail account. In short, this means you'll be able configure Gmail to easily keep your account in sync with your home and work PC, mobile phone, and any other device used to access Gmail with.
IMAP is geek speak for Internet Message Access Protocol. It competes with POP3 access to your e-mail account. POP3, or Post Office Protocol 3, was designed to support offline e-mail access to your ISP or Web-based e-mail accounts and that's it.

For years Google and other Web-based e-mail services have allowed you to set up your desktop e-mail client such as Outlook Express to receive and send your Gmail messages using POP3. But that feature has its limits. Changes made to your account using Outlook on your home PC are not reflected anywhere else. For example, say you access your Gmail account from your desktop PC using POP access and read, delete, send, and sort messages. Those changes are not reflected on your Web Gmail account.
Now with IMAP any changes (sorting, deleting, reading, or otherwise) are reflected across all Gmail interfaces - be it using Outlook Express, your iPhone, or Web-based Gmail. For example if you create a folder and sort messages into it using your desktop Outlook Express client those changes show up on Web-based Gmail.
IMAP access to your inbox has been around for some time, but it is usually a feature companies charge for. Many big-name ISPs and services, including Comcast, Hotmail, and Yahoo, still offer only POP3 access. Other Web-based e-mail services such as FastMail offer IMAP service for a few bucks per month and are rare.
The only catch to using Gmail's IMAP service is it takes a few minutes of configuring access. Google has made things easy with this short video that will give you an overview of the service.
More detailed instructions for configuring your desktop e-mail client software can be found by logging into your Gmail account and clicking on the "Settings" link, and then choose the "Forwarding and POP/IMAP" tab, and scroll down to "IMAP Access" and click on the "Configuration instructions" link.
great tip.. thanks
I have a hotmail account and I use Microsoft Office Outlook Connector to read, delete, send messages, using Microsoft Outlook. The account type is MAPI (not sure if this is the same as IMAP) It works great, and its free :)
@ Buckwater
Well, if your using HOTMAIL with the free MAPI service it's got one additional feature for now, you can also sync your contacts with the mails. But if you pay for the MAPI service, i believe you could also sync your calendar, notes and so on...
Other than this i don't see much difference between IMAP and MAPI services.