Change email header .....

[Agus]

Hi guys,

All i wanna do this time is change the mail from: header to another
address...As my system is named after an internal network name and doesnt
resolv from outside my LAN..when i send an email, for instance when a user
registers, they received it with the systems internal address and they cant
reply it cause of course it will get bounced....So i wanna change the from
header to an address where i have a mail redirection account....I know how
to do it from telnet for instance..its simple..but as i send emails from a
script using the mail program..

I basically do cat welcome_msg|mail -s "Welcome..." user at mail

So i was wondering if there is a way to send this automated emails changing
the header from:
Perhaps theres another program or way...Im open to suggestions...

Thanks and cheers,
Agustin