When I'm logged in and use the "E-mail this user" link, the resulting e-mail doesn't seem to contain any information about my originating IP address. Hotmail adds a "X-Originating-IP: [123.123.123.123]" header to any outgoing mail, and I think this would be a good idea for Wikipedia aswell.

If an IP address is blocked from editing articles, can that address still be used for sending Wikipedia e-mail? Can it be used for registering new users? Is that good or bad?

I can only send Wikipedia e-mail if I'm logged in, but the outgoing mail has a "From:" header that contains the address I entered in my personal preferences and that address hasn't been verified, has it? Is that good or bad?

Theoretically, if my IP is blocked from editing, I think I could sign up as a new user "Jimbooo" and set my e-mail adress to that of Jimbo Wales, and start to send insulting Wikipedia e-mails to Wikipedia users I want to turn against Jimbo. The recipients would get a message "From: Jimbooo <...>" with no information about my IP.