Modifying SMTP requests

view story

http://www.linuxquestions.org – Hi, I have a situation that takes a little explaining. A homegrown application is attempting to send email to the SMTP server on localhost and it's attempting to send as a user that doesn't exist (and indeed is not on our email domain). The localhost SMTP server, sendmail, is configured to listen only on and to relay all mail to our actual mail server. Is it possible to modify the application's messages so that by the time they hit our public MTA, the message is being "sent as" an email address that I specify? In case it isn't obvious yet, I'm not that well versed in sen (HowTos)