1and1-dns.com has no MX records.
Question and response
Question
dig 1and1-dns.com. MX
Answer
The response has no answer records.
Authority
1and1-dns.com. 600 SOA ns-com.ui-dns.com. dnsadmin.ionos.com. 2011022080 28800 7200 604800 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0