|Define the From format||All versions|
UUCP software requires all messages to begin with a header line that looks like this:
From sender date remote from <host>
The sendmail program prefixes such a line to a mail message's headers if the F=U flag (F=U) is set for the delivery agent. Prior to V8.7, if the local machine supports UUCP, the $l macro must be supplied with "From ", sender, and date:
 Prior to V8.7 this behavior was supported only if UGLYUUCP was defined in conf.h when sendmail was compiled.
DlFrom $g $d
The rest of the information (the remote from <host> ) is supplied by sendmail.
Under Unix, in a file of many mail messages, such as a mailbox, lines that begin with the five characters "From " are used to separate one message from another. This is a convention that is not shared by all MUAs. The sendmail program appends mail messages to files under only two circumstances: when saving failed mail to the user's dead-letter file, and when delivering to a local address that begins with the / character. In appending messages to files, it uses the UnixFromLine ($l) option to define the form of the message separator lines.
For sites that use the Rand MUA (and that do not also use UUCP), the UnixFromLine ($l) option can be defined to be four Ctrl-A characters:
Dl^A^A^A^A O UnixFromLine=^A^A^A^A