INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :74.201.84.163

I can send and receive all emails through my account with the exception of emails sent to one company. I receive their emails without any issues. But I receive the following message every time I attempt to send them a message.

" INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :74.201.84.163 is not allowed to send mail as drcolourchipmobile.com"

Please help me resolve this issue asap.

Thanks!