blue.soltec.net has no MX records.
Question and response
Question
dig blue.soltec.net. MX
Answer
The response has no answer records.
Authority
soltec.net. 3600 SOA blue.soltec.net. hostmaster.blue.soltec.net. 1651672442 3600 600 86400 14400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0