how to change [email protected] to [email protected] for emails sent out

Hi,

I am using Perl to send out group emails using postfix, dovecot on
RedHat enterprise 5.

Even though I can change the sender full name from Apache to MyName
for the emails sent out from the server. But in the email header
details, it still shows from [email protected] instead of
[email protected].

The code in perl that I use is:
open (MAILHANDLE,"| mail $address -s \"$subject\" -- -F MyName \n");

This create the issue that it maybe filtered out by receipeint's spam
filter. Also, create a problem if the user directly reply the email.

I try to modify the ServerAdmin directive in httpd.conf. But still it
does not work. I could not find any related configuration directives
in postfix either.

Am I wrong in the perl coding ?

Can anyone help me on this? Many thanks!!!