Google refuses to accept mail from our domain, what should I do?

Question

gmail

Situation: the coder mistakenly launched a mailing list to a not very large number of addresses (our clients), but a very large number of times. As a result, Google refuses to accept mail from our domain. When I try to send it says:

This is the mail system at host domain.ru.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<[email protected]>: host gmail-smtp-in.l.google.com[64.233.164.27]
    said: 550-5.7.1 [x.x.x.x      12] Our system has detected that this
    message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam
    sent to Gmail, 550-5.7.1 this message has been blocked. Please visit
    550-5.7.1  https://support.google.com/mail/?p=UnsolicitedMessageError 550
    5.7.1  for more information. s19si15570516lji.163 - gsmtp (in reply to end
    of DATA command)

Answer 1

Follow the recommendations https://support.google.com/mail/answer/81126?hl=en
Configure SPF, DKIM, and DMARC for your domain.
And the DNS PTR record is correct.

Answer 2

check if the hit is in the blacklists,
especially zealous people can set it up this way

Answer 3

How do you connect the two events so accurately?
Sending a bunch of letters and a ban from Google?
I ask for all proger coders who are destined to become extreme for any glitch ...
Alas, ah, the harsh reality and nearness of the majority of the so-called. business owners.
What if Google has been collecting statistics on you for a long time, and now it decided to ban you anyway, but you do mailings one way or another.
If on the topic, then discard prejudices and go to the Yandex box, no matter how Yandex is school-student-shaped and long-thinking, but letters sent via the smtp protocol are still successfully received.

Answer 4

The site https://www.mail-tester.com/ will clearly tell you what is wrong with your letter. Send a letter to the specified address and see what's wrong with it.