rc79.3uu.net has no MX records.
Question and response
Question
dig rc79.3uu.net. MX
Answer
The response has no answer records.
Authority
3uu.net. 180 SOA rc78.3uu.net. hostmaster.3uu.net. 2025120211 10800 1800 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0