Richard Krehbiel <rich@kastle.com> writes:
   The original poster wants to correct a broken Sender: line. If the
   value that Emacs computes is wrong, (mine is wrong too BTW) then
   making a right one is better, no?
   
   Per Abrahamsen <abraham@dina.kvl.dk> writes:
   No. If you think it serves a useful purpose for the user to change the
   value of the Sender field, then you do not understand the purpose of
   that field.
   
   The Sender field contains the following information: The user has
   customized the from address. Here is the original, uncustomized value.
   Thus, if you customize the Sender field in any way, it will be wrong.
   
   Addendum by Justin Sheehy:
   Per's advice is true for all systems where the (user-login-name) and
   (system-name) functions accurately describe your identity and host in
   such a manner that they can be combined to form a meaningful address
   that could be used to reach you. Regrettably, this is not true in all
   cases.
   
   Gnus attempts to follow mail and news RFCs by adding a Sender header
   when it detects that you are sending a message with a From address
   that is different from what it has guessed your local email address to
   be.
   
   There are two situations in which this guess will be incorrect.
    1. (user-login-name)@(system-name) should be a valid email address
       for you, but Gnus is creating an invalid Sender field.
       In this case, your system is most likely misconfigured. You should
       not change your Gnus configuration. Instead, track down the
       configuration problem and fix it.
    2. Due to your mail-reading setup, (user-login-name)@(system-name)
       does not produce a value that is meaningful in any way. This is
       the case for many windows users and users with NAT-based home
       networks, for example.
       If this is so, then you should override the functions
       (user-login-name) and (system-name) in your ~/.emacs file.
       
   However, if you are trying to change your Sender header just so that
   you will not have a correct email address anywhere in your headers,
   you should think again. There is no good reason to send news or mail
   with incorrect and unreachable headers. Among other things, this is a
   rude and selfish way to attempt to reduce one's flow of spam. Please,
   do not alter your From or Sender headers such that they are not
   deliverable mailboxes.
   
   Take a look at http://www.interhack.net/pubs/munging-harmful/ for just
   a couple of the reasons not to munge your address.