fallback.tuxis.net has no MX records.
Question and response
Question
dig fallback.tuxis.net. MX
Answer
The response has no answer records.
Authority
tuxis.net. 600 SOA nsauth1.tuxis.net. hostmaster.tuxis.net. 2026021902 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0