Does Google Overcache Their DNS for Email?

3 points by mxuribe 3y ago ↗ HN

I recently moved away from GSuite (to a paid email proviuder), and while my new provider is working great...I am seeing the odd email or 2 slip back into the Google inbox side. All DNS (MX, SPF, etc.) had been updated to point to my new provider...and yet, every once in a while maybe once per 2 weeks, I see an email message show up in the google inbox. Thankfully, it is not an important email message; they all have tended to be marketing emails. But, has anyone else experienced this? My theory is one of the following: 1) One of Google's servers is stuck with old DNS info and still routing some emails to themselves/Google. 2) Or, some other DNS server out there is stuck sending messages towards Google...and Google is happy to receive them.

I still have access to the google account associated with the legacy GSuite, but it simply doesn't send (so that part at least works fine) - which is why i was able to discover this little bug. Am I the only one experiencing this? I'm trying to give Google the benefit of the doubt, and assume this is simply a bug, andf not some greater conspiracy...but would love to hear if anyone - especially those who moved away from GSuite - is seeing this too. Thanks in advance!

1 comment

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toast0 3y ago ↗

You should double check that all your DNS is correct, but if it wasn't, you'd probably see more mail going to the old settings.

The unfortunate truth is there's a lot of recursive DNS resolvers out there that cache for way longer than the TTLs. If you moved DNS servers at the same time as you moved mail servers, you may find that some DNS resolvers will cache your NS records for longer than they should too. If you can make your old DNS servers return NS records for your new servers only, that might help... or just encourage them to return errors.

There's also stuff like outgoing mail servers caching MX records; Microsoft Exchange used to cache records for the length of the process, although I think (well, hope) that's changed in the last couple of decades.