I am using Postfix as a gateway for my domain and need it to change or rewrite the Envelope From address to match the From header. For example, the From: header is "joe@domainA.org" and the Envelope From is "bob@domainB.com". I want Postfix to make the Envelope From "joe@domainA.org" before relaying it on. I took a look at the Postfix Address Rewriting document but couldn't find anything that matched my use case.
(In case you're curious why I need to do this: Gmail uses the same Envelope From when sending from a particular account, no matter which From: address you choose to use. I would prefer not to disclose the account being used to send the email. Also, it messes with SPF/DMARC domain alignment - see 4.2.2 of the DMARC draft spec.)