Sounds unbelievable, doesn’t it? Clearly Gmail use their Spam ‘detection’ as a non-stop alpha version test-system, there’s generally an alarming number of false positives in their Spam folder, or, wait, they don’t call it a folder, they *label* it as being spam.
I have been running my own mail-server(s) ever since the BBS/fidonet days in the 1990s, and I can assure you, the reader; I do know how email works, I know what each header in an email means, I know why and when it gets blocked, bounced, deferred, queued, tagged, blacklisted, you name it. Been there, done it all. And that’s why I’m so fed up with google’s attempts to monopolize the email-sphere by forcing all other mail service providers to jump through unpredictable hoops in order to avoid their false positive spam-tagging. Just because they’re a big name doesn’t mean they know how email works, in fact, most of their delivery-servers are blacklisted somewhere for a reason. Compare that with my score why don’t you.

Apparently Google wants the entire world to use Gmail, and Gmail alone. When you finally got used to their strange label- and filter-conventions, after years of sending each other huge attachments, Google forces you to pay for storage because now your mailbox is full. And they read your mail, for targeted advertising. So it’s all about the money after all! (You don’t say..)

Stop making yourself dependent on Google’s opinions, don’t use their servers for your email. Even if you do proper whitelisting, Google will randomly decide what to change whenever they like. Even if your sending domain has fully valid Reverse DNS (PTR) records for both IPv4 and IPv6, uses dmarc and DKIM, has a valid SPF record, a CAA record, uses DNSSEC, TLS everywhere, and has never sent out one spam mail, Google may still end up labeling your precious message as Junk. Maybe one day they decide they no longer trust or like the competition. This should be the common theme:
Use Gmail (or a google-domain), rely on Gmail, and be sure to miss important emails for life..