"Sender:" rewriting (again)

["Artur Urbanowicz" <Artur.Urbanowicz@man.lublin.pl>]

Hi,

The cf/crossbar.cf script in current form appends local hostname
to "Sender:" field if the field contains an address with local part
only (i.e. "Sender: user" in opposite to "Sender: user@domain"):

This behaviour is quite useful when local user submits a message with 
incomplete "Sender:" field.

However, appending local hostname to the "Sender:" field in message 
received from a remote system (smtpserver in MSA-mode!) can produce
totally invalid address.

Can anybody tell me, if router process can append to the incomplete
"Sender:" field a name of host from which the mail message came?
This would work for messages received from local and remote system.
Or maybe there is another, elegant solution?

Regards,
Artur Urbanowicz