[RawInfoSec]

You're clearly not understanding this.

Random checks do belong in a large scale mail system such as GMail. Their system only checks 1 in x emails for DKIM/SPF.

Could you imagine running DKIM/SPF checks on EVERY single email coming in? That would take considerable compute power, not to mention increasing memory requirements in a system built to minimize such things so that it can be scaled properly.

Your problem is simple. Make your own MTA compliant to any applicable RFC's and GMail will just work. Skipping important items like SPF and DKIM will ALWAYS cause intermittent issues with various other MTA's.

>> I'd be perfectly ok with all this if I had made changes on my end but I fail to see how not having made changes on my end this suddenly started happening and I'm supposed to be the one at fault.

You're making the assumption that every delivery is going to the same server, running the same code, which tests the same checks... every time. - It doesn't, and won't. Outcomes can change in a system designed to flex and deal with current problems.

[jacquesm]

> Random checks do belong in a large scale mail system such as GMail. Their system only checks 1 in x emails for DKIM/SPF.

I'd imagine google has by now figured out how to make a cache work.

> Could you imagine running DKIM/SPF checks on EVERY single email coming in?

No, but I can imagine keeping a set of cached data per origin address.

> You're making the assumption that every delivery is going to the same server, running the same code, which tests the same checks... every time. - It doesn't, and won't.

Indeed. Unreliable by design.