The IMAP support has been more or less broken since the very beginning. Their custom labels make folders behave in a non-standard way and the IMAP itself is terribly slow compared to every single other provider I've used. I used to have dedicated workarounds in my email automation scripts for their weird folder semantics, for even such trivial tasks as actually deleting an email as opposed to merely removing a label from it.

It's already unusable as far as I'm concerned.