qBittorrent official forums

Has anybody used it?
I had a mailbox there long time ago, but it's features (gmx allows regexp filters) were useless to me back then. Now, when I have lots of mail and gmail with it's pathetic filters can't keep up I'm thinking about going back to gmx.

Hmm, gmail spam filters? If anything I've had them too strict on a few occasions, like it can't figure out an email that was mailed to me isn't spam? But I haven't had any or either in the last month, at least.

No. Filters that sort mail based on subject/sender/etc.
Well. I've just rereged and they don't have regex anymore. I guess they should've not bought mail.com - bad for business.

Maybe thunderbird with some addon supports regex?

I bet some console email app could sort your stuff easily. (mutt for example)
Or as Sledge said Thunderbird. Or check out Claws-mail, Sylpheed.

You can just do it on client-side and keep your provider. Best solution IMO. (You will have to keep your settings backed up, though.)