RT sending emais www-data <www-data@rt-dev.com>; on behalf of; test@rt-dev.com in RT 4.2.1

Hi,
when I send an email to test queue to my RT the response email showing up in Outlook look like this: www-data www-data@rt-dev.com; on behalf of; test@rt-dev.commailto:test@rt-dev.com.
I would like to get rid of “www-data www-data@rt-dev.com; on behalf of;” so only test@rt-dev.commailto:test@rt-dev.com shows up in Outlook.
My RT is 4.21 running on Ubuntu 11.04 Natty. Sendmail version 8.14.4, Apache2 version 2.2.17, Postgres 8.4.
Can someone guide where to change the RT setting to change the email response from RT.
Thank
Maimr

when I send an email to test queue to my RT the response email
showing up in Outlook look like this: www-data www-data@rt-dev.com; on behalf of; test@rt-dev.com.

I would like to get rid of “www-data www-data@rt-dev.com; on behalf
of;” so only test@rt-dev.com shows up in Outlook.

You need to convince your MTA to allow the www-data user to set the
“Sender:” and “From:” headers to be the same thing.

In exim this is done in trusted_users = www-data

sendmail is set using -f I think, plus adding the user to a particular group?

Rob