Setting sender (newby)

Hi,

After trying to post to a newsgroup (using 'w', then editing message
etc.) I get a complain from tin saying something about an invalid
sender. It disappears after a couple seconds, but I can read it is trying
to use "[email protected]" as sender.

I have set this in tinrc:

    [email protected]

and that's also what I type in 'From:' line when editing that message.

Why is that default value being used?

Thanks,

Maurício