Inbound Domain Blocked by Policy - Open Level 3 [Edited]

Hello,

I am experiencing a persistent inbound email block from a legitimate external domain ([Edited: "Personal Information"]).

The messages are being rejected entirely by the Comcast inbound gateway server (resimta-a2p-651319.sys.comcast.net) with the following diagnostic error:
552 5.2.0 TnyIw8JZevDHYTnyIwE7bF Prohibited by policy.

Note: I am posting this from an alternate forum profile. The target mailbox experiencing the block is my primary @comcast.net email address associated with my account, which I can provide via Direct Message to the verifying employee.

All domain authentication records (SPF, DKIM, and DMARC) are passing perfectly on the sender's side. I have an open Level 3 Case No: [Edited: "Personal Information"], but the engineering callback has delayed, perhaps because of the weekend.

Could an official Xfinity Support team member please pull this Level 3 case number and escalate it to the Postmaster Engineering team so I can DM you the specific email address to get this policy block reviewed?

Thank you for some help in advance.

[Title edited: "Personal Information"]