osser.otrs.com has no MX records.
Question and response
Question
dig osser.otrs.com. MX
Answer
The response has no answer records.
Authority
otrs.com. 3600 SOA ns1.your-server.de. postmaster.your-server.de. 2026021900 3600 1800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0