+.PP
+.B packf
+makes an mbox-style delimiter by examining the first line
+of the message. If the first line is a \*(lqReturn-Path\*(rq
+field, its address and the current date and time are used. Otherwise,
+if the first line has an \*(lqX-Envelope-From\*(rq field, its
+contents (which should already be in the correct format) are used.
+Otherwise, a dummy address and the current date and time are used.
+.PP
+Messages that are packed by
+.B packf
+can be unpacked using
+.BR inc .