I’ve seen several reports of unexpected rejections for unauthenticated email to Google over IPv6 today. Unauthenticated mail over IPv6 is a bad idea, but Google usually spam folders it rather than rejecting it.
The Gmail status dashboard is reporting an issue “Some messages sent to consumer Gmail accounts are being rejected due to authentication enforcement” so something isn’t working as intended.
Last week I posted a link to an article discussing how Gmail builds defenses to protect their users from malicious mail. One of the things I found very interesting in that article was the discussion about how Gmail deploys many changes at once, to prevent people from figuring out what the change was.
Let’s take a look at what Gmail said.
I was looking for some references today back in old blog posts. This means I discover some old links are dead, blog posts are gone or moved, and information is lost.
In this case it’s a post by J.D. Falk on deliverability.com. The link is dead (it looks like the whole website is dead), but I found a copy of his post and am reproducing it here. I don’t have permission, because I can’t get permission from him, but the content is extremely useful and I don’t want it lost.
As an update to yesterday’s post, Gmail is contacting postmasters at domains signing with 512 bit keys to warn them of the upcoming changes. This message also clarifies “DKIM keys failing.” Messages signed with 512 bit keys or less will be treated as unsigned by Gmail in the next week or so.
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