Masquerade ONLY Envelope Sender

[mburgoon]

I am running sendmail as an SMTP server on port 25. I have several clients with their own domain that use this SMTP server to send emails. As a value added feature, I manage bouncebacks for my clients thus I am implementing masquerading with my sendmail config.

The only problem is that I need the FROM address to be my client's domain (so they can receive replies) and the RETURN-PATH (envelope address) to be my address (so I receive the bounces). For example:

FROM: user@theirdomain.com
RETURN-PATH: me@mydomain.com

Here are my relevant entries in my MC file I used to create my sendmail config file:
---
MASQUERADE_AS(`mydomain.com')dnl
FEATURE(`masquerade_envelope')dnl
FEATURE(`masquerade_entire_domain')dnl
MASQUERADE_DOMAIN_FILE(`/etc/mail/masquerade-domains')dnl
---
The /etc/mail/masquerade-domains files contains a list of domains that use my SMTP server.

Again the issue I am having is that BOTH the FROM and RETURN-PATH are being masqueraded. Everything I've found states that masquerading by default applies to the header address (i.e. the FROM) and the masquerade_envelope feature will also apply to the envelope address (i.e. the RETURN-PATH).

Is there anyway I can masquerade ONLY the envelope (i.e. the RETURN-PATH) but not the header address (i.e. the FROM)???

Thank you, any help is appreciated.