-
-If the pw_gecos field has this form, then the internal \fInmh\fR
-routines that find the username and full name of a user will return
-\*(lqfakeusername\*(rq and \*(lqFull Name\*(rq respectively. If
-the pw_gecos field for a user is not of this form, there will be
-no username masquerading for that user.
-
-This facility is useful if you are using POP, and wish for messages
-that are sent by users to appear to originate from the username of
-their POP account, rather than their username on the local machine.
-
-.ti -.5i
-maildelivery: %libdir%/maildelivery
-.br
-The name of the system-wide default \fI\&.maildelivery\fR file.
-See \fIslocal\fR\0(1) for the details.
-
-.ti -.5i
-everyone: 200
-.br
+.RE
+.PP
+If it is, the internal
+.B nmh
+routines that find the username and full name
+of that user will return \*(lqfakeusername\*(rq and \*(lqFull Name\*(rq respectively. This is
+useful if you want the messages you send to always appear to come from the name
+of an MTA alias rather than your actual account name. For instance, many
+organizations set up \*(lqFirst.Last\*(rq sendmail aliases for all users. If this is
+the case, the GECOS field for each user should look like:
+.PP
+.RS 5
+First [Middle] Last <First.Last>
+.RE
+.PP
+\*(lqusername_extension\*(rq, when specified on the \*(lqmasquerade:\*(rq line, allows a second
+type of username masquerading. If the user sets the
+.B $USERNAME_EXTENSION
+environment variable, its value will be appended to the actual login name. For
+instance, if I am \*(lqdan@company.com\*(rq, and I set
+.B $USERNAME_EXTENSION
+to \*(lq\-www\*(rq, my mail will appear to come from \*(lqdan\-www@company.com\*(rq. This is meant
+to interact with qmail's \*(lquser\-extension\*(rq feature, where mail sent to
+.IR user \- string
+will be delivered to
+.IR user .
+Likewise, those using
+versions of sendmail for which \*(lqplussed user\*(rq processing is active can set
+.B $USERNAME_EXTENSION
+to \*(lq+\fIstring\fR\*(rq. These MTA features are useful
+because they allow one to use different email addresses in different situations
+(to aid in automatic mail filtering or in determining where spammers got one's
+address) while only actually having a single account. Note that
+.B $USERNAME_EXTENSION
+is only appended to the username when \fIpost\fR is
+generating \*(lq[Resent\-]From:\*(rq lines and the SMTP envelope
+\*(lqFrom:\*(rq.
+.BR inc ,
+for instance, will not try to read from a maildrop file called \*(lqdan\-www\*(rq (to
+recall the earlier example).
+.PP
+\*(lqdraft_from\*(rq controls the most powerful type of address masquerading. Normally,
+when a user explicitly specifies a \*(lqFrom:\*(rq header in a draft,
+.B nmh
+uses it
+rather than constructing its own. However, to discourage email forgery, the
+SMTP envelope \*(lqFrom:\*(rq and a \*(lqSender:\*(rq header are set to the user's real address.
+When \*(lqdraft_from\*(rq is turned on, though, the envelope \*(lqFrom:\*(rq will use the
+address specified in the draft, and there will be no \*(lqSender:\*(rq header. This is
+useful when a user wants to pretend to be sending mail \*(lqdirectly\*(rq from a remote
+POP3 account, or when remote mail robots incorrectly use the envelope \*(lqFrom:\*(rq in
+preference to the body \*(lqFrom:\*(rq (or refuse to take action when the two don't
+match). Note that the MTA may still reveal the user's real identity (e.g.
+.BR sendmail 's
+\*(lqX\-Authentication\-Warning:\*(rq header).
+.RE
+.PP
+.BR maildelivery :
+%libdir%/maildelivery
+.RS 5
+The name of the system-wide default
+.I maildelivery
+file.
+See
+.BR slocal (1)
+for the details.
+.RE
+.PP
+.BR everyone :
+200
+.RS 5