ns-backup-ext.myactv.net has no MX records.
Question and response
Question
dig ns-backup-ext.myactv.net. MX
Answer
The response has no answer records.
Authority
myactv.net. 600 SOA ns1.myactv.net. root.ns1.myactv.net. 2025091501 3600 600 1209600 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0