Any way to associate an email with a client?

I’m just testing EMclient out, and it is very impressive, but I keep finding some things I want that I don’t see how to do. This time it is to associate an email from one contact with another contact? I’ve seen that a person will have history. Say I purchase something for a client, or deposit a mobile check from a client. I get an email from the bank confirming the deposit or the wholesaler confirming the purchase. I’d like to associate that email from those companies, with the client who paid me or bought the merchandise so it appears in their history.

Maybe the search is so powerful, this is unnecessary. I haven’t studied the search function yet.

I may have solved this issue. Is there any reason not to have 100 or more tags? My idea is to create a tag of the clients name. Then I can search by tag and also see as I scroll through. Perhaps not as good as a link to a client, but still, a way to associate both emails and calendar events and potentially tasks with a particular client. Has anyone managed 100 or so tags and will that work?