When neither the allnet nor the metoo options are checked, your email address is only included in the To and Cc fields of a Reply to All in the form yourname@host.
For example, suppose you receive a message with this header:
From: salmon@sea Fri Aug 23 10:36:21 1991 To: yourname@machine, yourname@host, tuna@ocean
The To field of your reply would look like this:
To: yourname@host, tuna@ocean, salmon@sea