Outgoing mail spam issue

Mails that contains our domain-name are blocked.
Messages can be like:
"failed: host ppamail.s.thehostingplatform.com (31.216.35.57)
said: 550 5.7.1 Rejected by spam filter (2a276233-d9f2-11eb-9996-000c299e362c)"
or
"Failed: A message could not be delivered.
failed recipients"

Job: Find cause of this block and resolve it.

I am avaliable to share computer for testing (TeamViewer)