_q.ironport.com has no MX records.
Question and response
Question
dig _q.ironport.com. MX
Answer
The response has no answer records.
Authority
ironport.com. 3600 SOA ns1-93.akam.net. stbu-hostmaster.cisco.com. 2026020506 14400 900 2419200 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0