itxplain.nrw.net has no MX records.
Question and response
Question
dig mail1.itxplain.de. MX
Answer
The response has no answer records.
Authority
itxplain.de. 86400 SOA ns1.mainns.de. info.domains.resellerinterface.de. 1772668800 14400 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0