Does anyone know how to change the envelope-sender setting on SendMail and if so how?

Well I am  getting the right direction but that URL you provided is far from complete.
I have to admit my abilities with sendmail are a bit limited.

I think I will need a more step by step answer on this one.
The sendmail is installed from yum and has all the defaults in place currently if that helps
Also I have a sendmail O'Reilly book from years ago if that will help
I it talks about v8 m4 configuration though I do not understand this very well
The files that talk about masquerading are:
sendmail.cf
sendmail.mc
submit.cf
sendmail.mc

virtusertable
also:


I see the first level of masquerading maybe using the
/etc/aliases  file to mask users from being exposed but would that be enabled by simply
changinging sendmail.cf file:
# location of alias file
O AliasFile=/etc/aliases

Note its odd O is used instead of 0(zero)  which is surprising I would have guessed
that meant it was disabled. But upon more reading I realized O(oh)
meant Define an Option, however it does not appear to be working because
the user sending the emails is already defined in the /.etc/aliases file
yet the email envelope shows the aliased user e.g www
so I am at a loss to understand that.

Also
Also much of the text in your link seems to point to the sendmail.mc file
Perhaps a good sample sendmail.mc file may shed some more light on this
and how the link you supplied truly works
Would you have such an example file??

There was a line:
dnl FEATURE(masquerade_envelope)dnl

according to the book there needs to be a file: as  ../feature/masquerade_envelope.m4
but no such file exists. I guess that means it is undefined by default?

Maybe its me but those instructions lack a lot  with no examples and there is no mention of the  file name: sendmail.mc . Its all extremely cryptic.

I will try what yo suggest but I have a few questions:
given the domain I wish to maquerade as is:  xyzdomain.com
MASQUERADE_AS(the-domain.tld)dnl
the-domain.tld  - What is that  (what does .tld signify?) ? 'xyzdomain.com' or just:
MASQUERADE_AS(xyzdomain.com)dnl

FEATURE(masquerade_envelope)dnl
Does this file: ../feature/masquerade_envelope.m4  get generated via the m4
cmd: m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf  ?

FEATURE(masquerade_entire_domain)dnl

I imagine the text below should be
MASQUERADE_DOMAIN(xyzdomain.com or 'xyzdomain.com')dnl

I am almost  there I only need to understand your above instructions just a bit more as described above. Thanks again!

> the-domain.tld  - What is that  (what does .tld signify?) ? 'xyzdomain.com' or just:
tld == top level domain, eg. .com .net etc. Replace with Your domain.

All those are sendmail configuration statements encoded in m4 language. The command
 m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
interprets sendmail.mc as m4 language script and saved to sendmail.cf - the actual sendmail config file.

I am sorry for the delay in getting back to everyone. I hope to resolve this soon
I think the best solution I got which I have yet to test is ravenpl:

I do apologize  ravenpl. I just have not had time to try your solution yet - Please be patient with me. I am sure you will get the points for this question.

I hope to try your solution this coming weekend!

Patience please - it has been a hectic time. I will try to get to this Monday!

I am almost ready. I should have this by the 4th of January 2010.

Just so you know give my xyzdomain.com domain
I am planning to substitue:
MASQUERADE_AS('xyzdomain.com')dnl
FEATURE('xyzdomain.com')dnl
FEATURE('myhost.xyzdomain.com')dnl
MASQUERADE_DOMAIN('xyzdomain.com')dnl

I hope I have that right??