I’ve got multiple email accounts on my domains, as well as gmail accounts, as well as an icloud account and a work account that uses a cloud based exchange server. In this mix, I have multiple machines – Windows, Linux and OSX all running and accessing the same accounts in real time. The Beast (my windows box) runs all mail as POP to download hard copies of my email so if needed – I’m not dead in the water if the remote server or internet access is unavailable.
OSX and Linux access my email using IMAP – so that they are always updated with the same information regardless of which machine that I’m using.
I love the fact that I can sync my Contacts, Calendar, Notes, Reminders with OSX – and then use Thunderbird to link IMAP with the exchange server for e-mail. This keeps my inbox clean – and when I get a email – the dock notification is specific to Thunderbird and I know it’s work related. You don’t need to use the Thunderbird Extension (“ExQuilla”) that is full of bugs and features and costs $10 annually.
So, I use Apple’s Mail in OSX for everything except exchange email which is sync’d with Thunderbird via IMAP, with the other integration services provided by OSX.
This works for me.