ns3.intercom.com.sv has no MX records.
Question and response
Question
dig ns3.intercom.com.sv. MX
Answer
The response has no answer records.
Authority
intercom.com.sv. 86400 SOA ns1.intercom.com.sv. hostmaster.intercom.com.sv. 20200809 86400 7200 3600000 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0