customers.tuxis.net has no MX records.
Question and response
Question
dig customers.tuxis.net. MX
Answer
The response has no answer records.
Authority
customers.tuxis.net. 86400 SOA nsauth1.tuxis.net. hostmaster.tuxis.net. 2026022601 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0