mainns.de has no MX records.
Question and response
Question
dig mainns.de. MX
Answer
The response has no answer records.
Authority
mainns.de. 86400 SOA ns1.mainns.de. info.domains.resellerinterface.de. 1769416645 14400 3600 604800 86400
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0