mail.ybaca.net has no MX records.
Question and response
Question
dig mail.ybaca.net. MX
Answer
The response has no answer records.
Authority
ybaca.net. 86400 SOA ns-2.awsdns-00.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0