The only thing you can do at postmaster.google.com is to verify your email address with google.
If it will work? I don’t know. I verified all my domains in the last couple of years.
What’s the history of the domain name. I have a user, from which her site was hacked a couple of years ago. It sended lots of abuse mail. It took months before sites as google where accepting her mail as normal.
The other thing, you can do is to change the DMARC Record, to get reporting and a strict acceptance of email from only the hosts with the correct dkim/spf records. I personally have the domain name “doofpot.nl”, for more than 20 years. But with dmarc reporting, i still see sometimes a lot of spams ended trough other hosts.
_dmarc.some_domain.nl descriptive text “v=DMARC1; p=reject; rua=mailto:email@example.com_domain.nl; ruf=mailto:firstname.lastname@example.org_domain.nl; pct=100”
Which says: reject all the mail, not send trough box.my_domain.nl, if possible, give me forensic reports (for all the mail).
(create also an alias for ‘dmarc’
You 'll receive mails, mostly from google, telling it has accepted or rejected mail.
If google accepts the mail, but it’s locally moved to the spam, it’s up to the recipient users to learn google to accept the mail, by moving out your mail from spam to inbox
(in google meanings: remove label SPAM)