-The third way is controlled by the \*(lquser_extension\*(rq value of \*(lqmasquerade:\*(rq line
-of
-.IR mts.conf .
-When that's turned on, setting the
-.B $USERNAME_EXTENSION
-environment variable will result in its value being appended the user's login
-name. For instance, if I set
-.B $USERNAME_EXTENSION
-to \*(lq+www\*(rq, my \*(lqFrom:\*(rq
-line will contain \*(lqDan Harkless <dan+www@machine.company.com>\*(rq (or
-\*(lqDan.Harkless+www\*(rq if I'm using mmailid masquerading as well). Recent versions
-of
-.B sendmail
-automatically deliver all mail sent to
-.IR user + string
-to
-.IR user .
-.B qmail
-has a similar feature which uses '\-' as the delimiter by
-default, but can use other characters as well.
-.PP
-The fourth method of address masquerading is to specify a \*(lqFrom:\*(rq line manually
-in the message draft. It will be used as provided (after alias substitution),
-but normally, to discourage email forgery, the user's
-.B real
-address will be
-used in the SMTP envelope \*(lqFrom:\*(rq and in a \*(lqSender:\*(rq header. However, if the
-\*(lqmasquerade:\*(rq line of
-.I mts.conf
-contains \*(lqdraft_from\*(rq, the SMTP envelope \*(lqFrom:\*(rq
-will use the address given in the draft \*(lqFrom:\*(rq, and there will be no \*(lqSender:\*(rq
-header. This is useful in pretending to send mail \*(lqdirectly\*(rq from a remote POP3
-account, or when remote email robots give improper precedence to the envelope
-\*(lqFrom:\*(rq. Note that your MTA may still reveal your real identity (e.g.
-.BR sendmail 's
-\*(lqX\-Authentication\-Warning:\*(rq header).
+The second way is to supply a \*(lqEnvelope-From:\*(rq line. The value
+of this field will be used as the originating mailbox identity when
+submitting the message to the mail transport system. This will override
+both the value of the \*(lqFrom:\*(rq line and a \*(lqSender:\*(rq line
+(if one is supplied). The \*(lqEnvelope-From:\*(rq line is allowed to
+have a blank value; if the value is blank, then the mail transport system
+will be instructed to not send any bounces in response to the message.
+Not all mail transport systems support this feature.