Optional features to help administration of Mailing-Lists

When delivered copies of a message to a mailing-list are bounced,
original recipients' addresses should be reported in the bounced messages.
But no information on original recipients' addresses are sometimes shown
and administrators can not identify the original addresses in such cases.
So, if original recipients' addresses can be included in the least reported
information (e.g. To: header field or envelope sender address), we will
be able to identify original recipients' addressess.

If -1 option is specified to the smtpfeed, the smtpfeed will stop SMTP
piggy backing on delivery (does not send a message for two or more
recipients in one SMTP transaction). In this case, header or envelope of
each copies of a message can be modified for each recipients in a list
to include original recipient's address. There is -F option to make the
smtpfeed modify them.

1) -F option

 If -F option is specified once, the following field will be inserted
 to header part of each copies of a message which are sent to each
 recipients in a list:
	To: (original recipient in envelope at HOST) RECIPIENT
 Here, HOST is name of a host on which smtpfeed running, and RECIPIENT
 is envelope recipient address on delivery of the copy.

2) -F -F option

 If -F option is specified twice, envelope sender address of each
 copies of a message for each recipients in a list is changed like:
	SenderUser+RecptUser=RecptDomain@SenderDomain
 Here, original envelope sender address is SenderUser@SenderDomain,
 and original envelope recipient address is RecptUser@RecptDomain.
 If envelope sender address is <>, this address translation will be
 suppressed.
 This conversion style can be changed with -S option.

-F option is effective if -1 option is also specified. But -1 option
is not required always (-1 option raises network traffic). So, the
following configuration can be used instead of setting -1 option:

1) -S /path option

 /path is location of a file in which envelope sender addresses are
 written.  When one of addresses listed in the file matches with
 envelope sender address of a message which the smtpfeed received,
 -1 option will be assumed automatically.

2) X-smtpfeed: header field

 If X-smtpfeed: field exists in the header part of a message received
 by the smtpfeed and value of the field includes '1', -1 option will
 be assumed automatically, and X-smtpfeed: field will be deleted by
 the smtpfeed.

These features are just for house keeping management of mailing-lists.
