Right now its a gmail box but sooner or later I want it to scale.
I want to sync a copy of a live personal mailbox (inbox and outbox) somewhere else, but I don't want to affect the unread state of any unread messages.
what type of access will make this easiest?  I can't find any information if IMAP will affect the read state, but it appears I can manually reset a message to unread.  Pop by definition doesn't affect unread state but nobody seems to use pop to access their gmail, why?
Nobody uses POP because typically they want the extra functionality of IMAP, such as tracking message state.  When that functionality is only getting in your way and needs workarounds, I think using POP's your best bet!-)
get email unread content, without affecting unread state