k13.starfall.com has no MX records.
Question and response
Question
dig k13.starfall.com. MX
Answer
The response has no answer records.
Authority
starfall.com. 60 SOA ns0.pancil.net. sysroot.pancil.net. 2026012602 3600 1800 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0