I have been trying to figure out how to programmatically check if a gmail account exists. Almost all searches lead to validation services like xverify or EmailOversight where you validate any email address on a cost per request basis.
What I am interested in is a way to do that directly, without a middleman. In other words, how do these validation services do it? Seems like there should be some sort of an API that google provides for those guys to ping to see if an email address is valid.
Please note that I am not interested in checking the syntax of an email address. So I am not looking for some kind of a regex solution.
Also, what I have tried is connecting to gmail.com MX record domains (e.g. alt3.gmail-smtp-in.l.google.com) and trying to extract the validity of an email address by running simple SMTP commands. Essentially what this article suggests: https://www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email/
But I cannot do that for any kind of volume. Gmail will start blocking your connection attempt after a certain number of connections. So that method is not scalable. That's why I feel like there has got to some other way.
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Here is why this question is different from How to check programmatically a email is existing or not
That post provides only one solution, and it's one I have already tried - using SMTP commands. Google will NOT allow to do that on any kind of scale. If I only had to validate a few emails, then that would be a sensible solution, but if I have 10,000, it is not.