mail.webhosting.systems has no MX records.
Question and response
Question
dig mail.webhosting.systems. MX
Answer
The response has no answer records.
Authority
webhosting.systems. 1800 SOA root-dns.netcup.net. dnsadmin.netcup.net. 357 900 900 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0