Gmail is one of the most popular web-based email services, mainly due to its ability to leverage Google’s branding and search, in addition to its ease of use. And while Google has made Gmail a popular mobile and desktop web destination, one of the places where it has not been as up to speed has been in its support of the IMAP protocol for reading email and managing the inbox. Today, Google has begun to roll out IMAP support as a free service to all Gmail users.
The relevance of IMAP support for mobile users is that Gmail now more more accurately states the condition of an inbox. If an email is read on the mobile device, then it will also show as being read from the desktop browser.
Unlike POP email, using IMAP requires the user to stay connected and the email will always remain on the server. In the case of Gmail, the placement of the email on Google’s servers has always been the case, but users will want to ensure that they have the appropriate data plan for using this enhanced email option.
Currently, most desktop and mobile devices except Palm OS models accessing IMAP through VersaMail are supported (view complete list). No further information about future Palm OS support has been given. Specific setup information for using Gmail via IMAP on the iPhone has also been given.
To enable IMAP functionality for a Gmail account, view the "Forwarding and POP/IMAP" tab under Settings. More information about IMAP support in Gmail can be found through a Google Help Center article.
Currently, this service isn’t available to all Gmail users, but Google says it should be in the next few days.
More information about IMAP, and its advantage and disadvantages to POP is detailed at Wikipedia.