reg Mailx command or masking of mailid

I am using the mailx command of Unix through which I am able send mails but the problem is the from mail ID is automatically buit by unix as the (UNIX Box Name:---------------------------------) to mask the from id the option used by mailx is -r but for some security reasons this is blocked by the client. So is there any other way through which the from mail id can be masked to a valid email id ?
The example of how the mail looks when its sent :

-----Original Message-----

From: Support1 rsetl () [mailto:billset@qdcb204.mobe.becom.be]
--------------- This thing has to be masked to valid email id

Sent: 05 February 2004 15:12
To: RISHNAN (BMB); Pi_M@info.com;
Subject: Electronic Document: CO flow : 200401

Kindly please help.

Thanks for u r time and patience .

Many Thanks
Narendra babu

If you can use sendmail instead of mailx command then we have the post here sendmail