Hey Francesco, many thanks! Yeah I definitely did consider procmail, especially given that I used it during several years.
At some point, though, I started to use Mutt's imap support and, as weird as it may sound I tend to like this way of dealing with mails. I really don't know what made me switch! Perhaps it was because I liked knowing the total number of e-mails I have to deal with. Not to say your solution is not worth it, it definitely is! I'm still considering reporting the issue at their accessiblity desk, because for me it is an accessibility issue (I am blind, that' I think why emails are so crucial for me). I'd be happy to mention your question and even to Cc you if you wish, just let me know. Best wishes, Seb.