Hello @LarryLopez-8186 ,
I believe this is a duplicate of the question https://learn.microsoft.com/en-us/answers/questions/36743/remote-server-returned-550-57705-service-unavailab.html
The short answer is that the outgoing mails for your tenant are blocked and the O365/M365 administrator will need to go to Microsoft support to get this unblocked. Please check the article for more . https://learn.microsoft.com/en-sg/office365/troubleshoot/antispam/tenant-has-exceeded-threshold
In future if you have any query related to Office365 / Microsoft 365 , You can reach out to the Office365 / Microsoft 365 tech community here. Hope this helps.
Thank you.