[otrs] how to set the 'sender' on mails from OTRS (to avoid 'on behalf of')

hi - can anyone help me control the sender/from infomration on mail sent by otrs? recipients are seeing mails arrive from (as seen in MS Outlook): 'OTRS [otrs@server.mydomain.com] on behalf of My Company [info@mydomain.com]' In the mail header, there is From: My Company Sender: OTRS i want to remove the 'OTRS [otrs@server.mydomain.com] on behalf of' bit - ie set the sender as 'My Company ' any ideas? i've searched config.pm and much else... i'm using otrs 1.1.3 on debian with exim as the mailer. thanks ben