_dmarc.3uu.org has no MX records.
Question and response
Question
dig _dmarc.3uu.org. MX
Answer
The response has no answer records.
Authority
3uu.org. 180 SOA rc78.3uu.net. hostmaster.3uu.net. 20251211 10800 1800 604800 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0