-Added by
-.BR post ,
-contains the address of the author or authors
-(may be more than one if a \*(lqSender:\*(rq field is present). For a
-standard reply (using
-.BR repl ,
-the reply address is constructed by
-checking the following headers (in this order): \*(lqMail-Reply\-To:\*(rq,
-\*(lqReply\-To:\*(rq, \*(lqFrom:\*(rq, \*(lqSender:\*(rq.
+This header is filled in by default with the system's idea of the user's local
+mailbox. This can be changed with the
+.B Local\-Mailbox
+profile entry.
+It contains the address of the author or authors (may be more than one if a
+\*(lqSender:\*(rq field is present). For a standard reply (using
+.BR repl ),
+the reply address is constructed by checking the following headers (in this
+order): \*(lqMail-Reply\-To:\*(rq, \*(lqReply\-To:\*(rq, \*(lqFrom:\*(rq,
+\*(lqSender:\*(rq. A \*(lqFrom:\*(rq header MUST exist when the message is
+sent to
+.BR post,
+otherwise the message will be rejected.
+.RE
+.PP
+.BR Envelope\-From :
+.RS 5
+Used by
+.B post
+to specify a value for the sender's envelope address to the mail transport
+system. If omitted,
+.B post
+will use the value of the \*(lqSender:\*(rq or the \*(lqFrom:\*(rq header.
+See
+.IR send (1)
+for more details.