Moving Gmail account from POP to IMAP with Mail.app

Question

I've been using POP to access my Gmail account using Mail, but I want to switch to IMAP to synchronize read emails with the web interface, and, most importantly, with my iPhone (which is already using IMAP). However, I know that Gmail has a nonstandard IMAP implementation which exposes multiple copies of the same message as different messages in different mailboxes, and I want to avoid keeping multiple copies of messages on my HD. OTOH, I do want to keep at least one copy, because I like having a full backup of my email.

I need advice on:

1. The best way to setup IMAP so I have a backup of every message, but no duplicates (or as few as possible);
2. The best way to handle the migration so that, at the end, the messages I have downloaded via POP are associated with the IMAP mailbox (replaced, maybe), but the messages that I have marked as read in Mail.app so far need to stay marked as read (ie the read status needs to get carried over).

I am especially interested in hearing from people who have attempted this before, since I suppose there may be pitfalls that you only understand with practical experience.

I am on Lion and I'll be using Mail 5. It seems that Mail 5 might have some new support for Gmail's specific brand of IMAP, though I don't know how extensive. iOS Mail, for instance, has an "archive" button instead of "delete" for Gmail accounts; Mail 5 now has an "archive" feature too, and it would be nice if it synchronized with Gmail's idea of archiving.

Answer 1

Why not use Exchange Activesync? This way your mail would be pushed imediately instead of waiting for imap polls. Also, in the case of your phone, contacts would be synced two-way over the air, much like mobileme does.

http://www.google.com/support/mobile/bin/answer.py?answer=138740&topic=14252

I believe (not tried it yet) but you could set Apple Mail up with your gmail account this way as well.