Howto edit email header

[koeppe]

Hi,

I have a web service with email forwarding. Unfortunately are emails from hotmail, gmail etc. forwarded through our server classified as spam at the receiving server.

I have been looking for a solution and it seems that if I add 'sender: [email protected]' the the email header the emails are accepted.

Is there a way to add the sender to the email header on mails send through plesk (qmail) ?

regards,
Jakob