Rewrite 'from' header to enable forwarding to overcome dmarc restrictions?

[Furnish, Trever G]

My company has a subset of users for whom we are still doing "dumb forwards", and this practice is now resulting in undeliverable mail thanks to the recent change of dmarc policy published by AOL and Yahoo.  I thought I could work around this by passing the mail for these users through a mailscanner system (just as it was on the verge of finally being decommissioned) and turning all mail into attachments.  It looked promising, but it fails, because MailScanner still is using the original From and To message headers on the new message it creates even for attachments.

Is there any way anyone can suggest to get around this?  At this point I'm even pondering just modifying the mailscanner code directly or trying to hook in an 'always called last' function to modify the message.

What's happening now:
	MailScanner creates a new message and attaches the original.  In both the new message and the attached original, there is a "From:" header saying e.g. "From: bob at aol.com".

What I wanted to happen:
	Mailscanner would create a new message and attach the original.  In the NEW message the From header would have value "postmaster at mydomain.com" or some such.

Any suggestions? 

--
Trever Furnish, tgfurnish at herffjones.com
Solutions Architect
Herff Jones Server Solutions Group (SSG)
Phone: 317.612.3519  Cell: 317.366.9258