mail being blocked because of DLP policy?

There's an email that's being blocked everytime and in the message trace details it only refers to the responsible mail flow rule by a hexadecimal string.

In a section called message events, there's an item that says

Reject message. Transport rule: '', ID: ('E7B3F3CA-770F-4030-87D1-371FFCAD7195'), DLP policy: '', ID: (00000000-0000-0000-0000-000000000000).

the ID here is the hexa string of the mail flow rule.

There are some mail flow rules I set up to block bitcoin spam and phishing emails but nothing that would obviously block this email.

There's nothing in mail flow that identifies rules by hexa string and I haven't done anything with nor know anything about DLP policies. How do I address this issue?