_sip._tcp.adobe.com has no MX records.
Question and response
Question
dig _sip._tcp.adobe.com. MX
Answer
The response has no answer records.
Authority
adobe.com. 300 SOA exfer-vip-01.corp.adobe.com. hostmaster.adobe.com. 11352 1800 600 2419200 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0