nlmail.nextlayer.at has no MX records.
Question and response
Question
dig nlmail.nextlayer.at. MX
Answer
The response has no answer records.
Authority
nextlayer.at. 86400 SOA ns.nextlayer.at. hostmaster.nextlayer.at. 3021134910 10800 900 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0