mail4.verisign.com has no MX records.
Question and response
Question
dig mail4.verisign.com. MX
Answer
The response has no answer records.
Authority
verisign.com. 86400 SOA av1.nstld.com. mdnshelp.verisign.com. 1771783480 300 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0