One feature I like very much about Opera Mail is that you can have learnable filters for any purpose. So not only can you filter spam messages but also messages that your friends sent you or info mails from web platforms without having to enter each and every mail address you want to filter. It actually works quite satisfying and you can combine it with string filtering, too. It does a few mistakes in the beginning but then improves quickly after you have removed some of the false positives.
However, there are a couple of drawbacks with the Opera Mail module.
The filters are only ‘virtual’. So, with IMAP there is no easy way of mirroring the filtered structure back on the server and when I’m using webmail I’ll see the whole unfiltered mess in the inbox folder.
Opera’s not using the OS X address book — and neither does it use ldap (which is not too important for me at the moment).
So, I’m not specifically looking for a Thunderbird solution here, a way to fix things in Opera or Apple Mail should do as well. Or some other E-Mail program I don’t even know about yet. (So, to be clear, I’d like to have: OS X Address Book integration, Learnable filters for any type of filtering, Ability to push filtered folder structure to the IMAP server) But I thought like, if it is possible then most probably there would be an add-on for Thunderbird available.