sendmail question

[David M. Siegel]

I would like to invoke sendmail to send a message with the receipient
specified in the command like, like 'sendmail foo', and have sendmail
set the sender to the contents of the 'from:' line in the message. I
was wondering if this is possible? 

A related question: when I run the mail queue by hand, with 
'sendmail -q', all locally delivered messages get a unix 'from ' line
with the invokers userid, and not the expected contents of the 'from:
line in the message. Is there any way to get around this problem?

Thanks,
-Dave