Gmail scanned my contents and shadow banned my emails

I used gmail to send a few emails for customer research purpose. These all are valid email addresses with people who have expressed interest in receiving research. I noticed that after some time Gmail stopped delivering but shows all emails as "Sent".

I tried to test on my another email id. It appears that as soon as I use my customer research content, Gmail does not deliver and shadow bans me. But, sending email with subject and content as "test" gets delivered.

I simply don't understand why Google is becoming such a disater day by day? Any ideas how to bypass shadow ban?

Edit: Now I am unable to receive any email on account used for sending customer research.

You probably explicitly broke some T&C and your account is heading to being closed. My guess would be, a recipient objected, and the s/w is closing in on you.

Google takeout is now very important. If you haven't started, its time to visit takeout.google.com and make sure you have a backup of all your data.

Your experience with "test" emails going through but not others reminds me of a theory I have wondered about. Do ISPs temporarily prioritize traffic for customers who visit speed test websites?

Could you post an example of one of these emails you're trying to send? I know you've stated that they've opted in to receive these emails, but Google doesn't know or care about that, if you repeatedly trip their spam filter for outbound mail then I'd wager your gmail account does not have long before it's banned completely.

As others have said, use Google Takeout to make a copy of your data - I would also take the time to back up any other accounts e.g. personal ones and make preparations for their banning as well, as Google have been known to ban associated accounts [1].

[1] https://www.reddit.com/r/Android/comments/b10c71/google_play...