mx01.1and1.com has no MX records.
Question and response
Question
dig mx01.1and1.com. MX
Answer
The response has no answer records.
Authority
1and1.com. 600 SOA ns-1and1.ui-dns.com. dnsadmin.1und1.de. 2013096354 10800 3600 604800 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0