Emails sent from a specific domain to my outlook mailbox bounced back.

Bouncing Message that was sent to the domain stated:
(SMPT Error 550 SC-001) Mail rejected by Outlook for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help.

I've checked my email filter and the sender is in the save sender list. Please help resolve this issue. Thank you.

JWK