gslb.verisign.com has no MX records.
Question and response
Question
dig gslb.verisign.com. MX
Answer
The response has no answer records.
Authority
gslb.verisign.com. 60 SOA gslb.ilg1.verisign.com. hostmaster.gslb.ilg1.verisign.com. 2026021024 10800 3600 604800 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0