Brilliant. At least you could expand your e-mail forwarding scheme ("Email Notes to"-mail feature), so that it could support tags in the mail body / header. For example if I want to automatically forward an e-mail to a specific notebook, I could 'tag' the message by prepending #nb:name_of_notebook to the body or header. That could work universally. Just my two cents…
OSX Mail plugin
in Evernote for Mac Requests (Versions 7.14 and under)
Posted
I don't know if you are aware, but you can assign an emailed-in note to a notebook and tag it by appending terms to the subject line, see https://evernote.com/contact/support/kb/#!/article/23480523