sftp.webcrf.net has no MX records.
Question and response
Question
dig sftp.webcrf.net. MX
Answer
The response has no answer records.
Authority
webcrf.net. 900 SOA ns1.p201.dns.oraclecloud.net. hostmaster.oracle.com. 2026012701 10800 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0