www.rackspace.com.edgekey.net has no SRV records.
Question and response
Question
dig e13746.dscb.akamaiedge.net. SRV
Answer
The response has no answer records.
Authority
dscb.akamaiedge.net. 1000 SOA n0dscb.akamaiedge.net. hostmaster.akamai.com. 1772878889 1000 1000 1000 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0