Sending emails from personal mail server to google. What am I doing wrong?

Question

Mail server

good day everyone!
the situation is as follows, there is a domain with a static IP address . it runs a mail server. (before that, they used hosting from the company, now they decided to transfer the whole thing to themselves). it means that we set up DNS records because we constantly tested them through the application service for checking the mail server, deleted the IP address in all spam databases. screwed DKIM SPF DMARK through tester-mail shows 10/10 you have the most secure letter, you can send it anywhere. The PTR zone was also prescribed. But there was one problem .... letters are not sent to Google (@gmail.com mailboxes) on the Internet, I rummaged through everything that can be answered and did not find it, everyone advises the same link that does not really give anything. via Google feedback sent several letters for help to no purpose. and what it can be connected with is not clear ...
below error

<-- 550-5.7.1 [88.204.179.114      18] Our system has detected that this message is
  <-- 550-5.7.1 likely suspicious due to the very low reputation of the sending IP
  <-- 550-5.7.1 address. To best protect our users from spam, the message has been
  <-- 550-5.7.1 blocked. Please visit
  <-- 550 5.7.1  https://support.google.com/mail/answer/188131 for more information. h25si9133022lja.2 - gsmtp
  --> QUIT

Answer 1

it is necessary to register the reverse zone from 88.204.179.114 to argoresources.kz,
this is usually done by the provider who provided 88.204.179.114

Answer 2

To diagnose the work of mail, I use mxtoolbox and mail-tester

Answer 3

I have the same situation. How did you solve this problem??