[leephillips]

Sounds like I need to update my article. Thanks for this information.

But note that they are still violating the RFPs, if they rewrite headers for people who fail to jump through these hoops. They can implement their spam protections (if that's the purpose) while remaining compliant by rejecting the emails in question.

[Aelius]

Maybe I've misunderstood something, but if gmail didn't do this, what's to stop me from sending emails that look like they come from your address?

[leephillips]

Nothing. The standard allows you to put anything you want in the From: header. Sometimes I send emails from Santa Claus or God. The envelope information is still there.

[leephillips]

Actually, not "nothing." If the MSA doesn't like this, it is free to reject the email. But not to change its content.