If the metoo option is not checked, the message header of your reply depends on the allnet option. The allnet option determines whether your mail address is recognized in all forms that include your login address, or only in the form yourname@machine.
The allnet option only has an effect when the metoo option is not checked.
If the allnet option is checked and the metoo option is not checked, and you do a Reply to All, your address is not included in any form in the To or Cc fields of your reply.
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: tuna@ocean, salmon@sea
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