I am currently getting some emails with the error code 550 when replying to contacts this is an example: 

ERROR_CODE :550, ERROR_CODE :permanent failure for one or more recipients ( jackie.williams@cruiseplanners.com :blocked) 

I am also getting blocked:  550 5.4.6 Mail rate exceeded limit I click on unblock and I just sent like 12 emails and I am getting blocked again, I am not even close to the limit 500MB per day, our team already send email to support and call several times tu support and nobody answer, we also send an email to sales asking if we need to buy something so we don't get blocked... please advise...