[peterwaller]

SPF has another problem. I sent an email to someone recently @theirdomain.com. I subsequently saw by chance that the email was rejected because they were hosting @theirdomain.com with a random ISP but they had configured the mail to be forwarded to a mailbox in @gmail.com.

Gmail sees the email coming from @theirdomain.com's servers, rather than my server. Gmail checks the SPF record which doesn't match, and it rejects it.

I understand that this style of forwarding is anyway bad because gmail see's all email the user receives @theirdomain.com as coming from those servers, not their true origin. If @theirdomain.com receives (and forwards) any spam, it looks like a spammer to gmail.

[mwpmaybe]

The solution to this is SRS[0], but yes, not every mail-forwarder implements this (correctly), and it seems to break DKIM. The good news is that an SPF soft-fail and a DKIM pass usually means a DMARC pass. More information here[1].

0. http://www.openspf.org/SRS

1. https://blog.fastmail.com/2016/12/24/spf-dkim-dmarc/

[jlgaddis]

Even with SRS, the "reputation" of the "middleman" (from Google's perspective) still suffers.

[hackuser]

Gmail needs to adjust to reality, not vice versa.