Have you considered sending your message to the Mailop mailing list?
I know that there are a couple of Gmail admins / coworkers that are subscribed to Mailop and will respond to issues like this.
Plus, it might also be a better forum and get more engagement / suggestions / gratitude by others learning from your toils.
On 03/31/2018 12:31 PM, Lindsay Haisley wrote:
At some point Amazon (amazon.com) started publishing a DMARC "p=quarantine" policy, which means that any email which gets redirected and hits my dmarc_shield piece is going to have its From address re- written to "postmas...@fmp.com" (fmp.com has a proper SPF record).
I'm sure that Amazon is just one of /many/ companies that are working with DMARC. - Seeing as how some ~> more governments are (going to be) requiring DMARC, I expect that we will see more of this.
I don't know what Gmail's policy is with regard to "p=quarantine" - whether it rejects such email outright or relegates it to the recipient's spam folder. I know that if the sending site publishes "p=reject", redirected email is refused by Gmail at the front door. I'll have to test the "p=quarantine" behavior.
I'm confident that Mailop subscribers can respond to this.
Here's the really annoying thing. My dmarc_shield processor rewrites the From header as per SOP for Mailman with the proper switch turned on. The From header address becomes "postmas...@fmp.com" with the original From address in the address comment (from xxx at yyz.com). If the email didn't already have a Reply-To address, the original From address is inserted as the Reply-To address. If a Gmail user replies to such an email, the reply goes to the Reply-To address, but Gmail **whitelists** the From address! Thereafter, any email which comes in with a munged From address is accepted, bypassing Gmail's otherwise pretty good spam filtering. I'm noticing a lot of spam email going out with From addresses for which a DMARC "p=reject" policy is published, which means that any such spam redirected to the Gmail user via FMP is also whitelisted. Bah! It's a fucking war zone out there!
I'm confident that Mailop subscribers can respond to this too. Probably including reasons as to why something is done.
I speculate that it's to prevent abuse of meaningless addresses being used in the From: address and causing replies to go somewhere other than back to the (purported) sender.
The only possible solution here would be to randomize the username portion of the rewritten From address, which makes the email look more like spam, and the Gmail user would end up with a whole lot of useless whitelisted address which would need to be deleted. Not to mention the fact that FMP's mail server might be blocked from sending ANY email to Gmail.
I initially thought about something like an MD5 hash of the (purported) From address. Though that still suffers from the multiple addresses being white listed. Despite that, I'd consider forwarding from a "forwarding" (sub)domain. Something to hopefully help articulate to the human looking at the complaints that the message is forwarded. Plus this I would expect this to help differentiate email reputation for fmp.com from the (sub)domain used for forwarding. (I don't know if a sub-domain would suffice or if it should be a different parallel / sibling domain, fmp-forwarding.com.)
-- Grant. . . . unix || die
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