apollo.ntis.gov has no MX records.
Question and response
Question
dig apollo.ntis.gov. MX
Answer
The response has no answer records.
Authority
ntis.gov. 1800 SOA blue.foundationdns.com. dns.cloudflare.com. 2397441063 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0