Undelivered Mail Returned to Sender : 550 5.7.511 Access denied, banned sender

ashraf2240 bootah 

Sorry if i misread the situation here; Just to confirm; the server responsible to send out emails, is setup with Office 365 SMTP Mail relay? or is it some third-party email solution not leveraging Office 365 settings? Also if you feel comfortable, can you please share the domain name using which you tried to send emails?

Thanks