mail500c7.megamailservers.com has no SRV records.
Question and response
Question
dig mail500c7.megamailservers.com. SRV
Answer
The response has no answer records.
Authority
megamailservers.com. 86400 SOA ns1.meganameservers.com. root.megamailservers.com. 509 86500 3600 3600000 345600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0