So what would be a good client on Windows ?
So I guess back to Opera Mail. Other ones like TB, Sylpheed don't cut it for me.. I guess they have UI and network actions within the same thread, and that makes them get stuck.
Also the modal UI blocks only the one sync queue - i.e. the one for contacts & calendars in that account. All other accounts including mails for that same account should continue syncing.
I'd love to help you with those issues - you can contact me at grafnetr@emclient.com
There was a thread on HN a few months back that talks about its unique security/password sharing model. It's clear that the developers put a whole lot of love into it.