Assigning contacts tags automatically to emails (sent and received)

I use tags extensively, both for managing contacts and emails. It is a lifesaver as tags help me manage my email addresses and organize my business activities and my social and personal lives.

However, I find it tedious to tag ALL my contacts only to find myself afterwards compartmentalizing my emails (by tagging them) using the same categories (either manually or according to rules).

I’m just wondering what could be the use of tagging all contacts into categories (beside the use of distribution lists) if this effort doesn’t lead to a better management (and filtering) of emails involving these contacts.

So, is it possible to apply contacts tags automatically to incoming and outgoing emails? In others words, would it be interesting for you to see your emails being tagged according to senders and recipients tags without having to use rules? This way mail will inherit tags from contacts by association.

Thanks for your comments/help.