A friend asked me the following, but since my Postfix-fu has not been exercised for years, I thought I should turn to you:
Mail for the organization (example.com) is handled by mail.example.com which runs postfix. There exists a second machine named eservices.example.com which sends email to a number of people. eservices.example.com is not using a smart host and is managing its own mail both incoming and outgoing. However whenever email@example.com sends mail to firstname.lastname@example.org, the sender gets re-written to email@example.com by mail.example.com. How can this be prevented?
I have the postconf output, but do not have permission to post it, so if you need the value of any variable, ask.