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  IMAP for Beginners  

This is for those considering using  Internet Message Access Protocol (IMAP) rather than the traditional Post Office Protocol (POP) for email transmission. 

The key difference between them is that POP configured email clients (e.g. Outlook, Outlook Express, Windows Mail) will retrieve any messages marked as unread on a remote server then set a flag to say that the message has been read, before optionally deleting the message from the server.  Once a message has the 'read' flag set it will never be available for downloading again.  IMAP clients work in a different way: they synchronize with the server so that one or more devices (e.g. PCs, Apple Macs, Blackberrys, netbooks) always maintain an exact copy of the messages held on a server. 

The benefit of IMAP over POP is that message conversation threads may be viewed in their entirety on multiple devices so you can send from any device and receive on any other with the message history being available on a third.  The disadvantage is that the way of working will initially be a little unfamiliar to those who have grown comfortable with the status quo.  Also, sufficient server space must be made available to avoid the frequent need for deleting old mail messages.

Below, I highlight the key usage differences using Google's Gmail product as an example.  Note that there will be minor differences between what follows and what the reader experiences as different clients - particularly Gmail's web interface, work in slightly different ways.

Deleting messages. 

Rather than clicking the red cross or pressing the delete key to have the message refilled in the Deleted Items folder, Google's IMAP will mark a message for later deletion (by striking through the subject text) and let it remain in situ.  At a later date the message is then purged (removed) either by virtue of the user activating a command from a menu or the clock ticking round to the 30 day anniversary.  To mimic the POP way of working you would need to move the message to be deleted to the [Gmail]Bin folder.
More explanation is available at mail client sites such as Outlook or Google.

Sending messages.

When you send messages using the Googlemail server, a copy may be found in the [Gmail]/Sent Mail folder. As this is synchronized between server and client in an IMAP configuration there is no point storing a duplicate so it is recommended that you disable sent messages from being held locally in your Sent Items folder. 

Folder hierarchy.

Although not strictly an IMAP difference, this may be a significant conceptual shift for Gmail users.  Messages are not filed in folders as is conventially done, in Gmail all messages have one or more labels attached and can be displayed according to those.  To retain a visual hierarchical display in Googles webmail interface look into 'Nested labels' in Google labs.

For general configuration settings see Google support
To see how client actions reflect in Gmail IMAP see Google support.
For Outlook specific differences see Microsoft Support.
To configure a Blackberry device see Blackberry Support.

I hope the above has not frightened anyone off IMAP as the differences between it and POP are not substantial, but it is best to go into these things with open eyes.  Before you make the decision whether to switch to IMAP why not [ask Eugene to] create a free test account and play around with it to see if you can live with the differences.

Please let me know how this page could be improved.