I’ve had a Gmail account since September 7th, 2004 and currently have 13096 conversations (and counting) in my “All Mail” box using up roughly 1GB of space. One of my first suggestions to the Gmail team was IMAP, and I am glad to see that it has finally made its way in.
The advantage of IMAP over POP is that you can see a list of your folders (or in Gmail’s case, tags) and emails that you can move around, mark read/unread, reply, forward, etc. right in your favourite email client, and any action will be synced with the server. Thus, you can mark mail as read, and label it some tags from Outlook, and Gmail will automatically do the same thing on their side as well. Also, since all the actions and mail are synced with the Gmail server, whenever you login from any client configured for your email, or from the Gmail web interface, you will see the same list of emails in the same tags. POP only allows you to get the mail (in one single inbox folder, relying on your client to filter any incoming mail), but any further actions won’t be synced up.
I’ve known that Gmail was going to add in IMAP a week or two ago while reading “Look out Outlook IMAP for Gmail is Coming” on GottaBeMobile, but I didn’t realize that I would get the functionality so quickly. So I found the IMAP feature in my Gmail today (I don’t use the web interface much) and I thought I’d try it out. It took a while to sync up all the folders and headers. Anyway, I’m still debating whether or not to keep it. I’m still trying to figure out how to archive mail from the inbox, and trying to get Outlook to download the entire messages from the server.