In my Z account I have disabled the storing of emailed contacts into the appropriate contacts folder.

But now I noticed those contacts are stored anyway!
Yesterday I mailed a new email address, and today I found that autocomplete proposes me that address!

How's that possible?

There's also another thing that sounds strange to me: for some contacts I have in my address book, when I open mail I see a "nickname" instead of the full name I compiled. And this nickname is usually the first part of the email address.