smtpe1.intersmtp.com has no MX records.
Question and response
Question
dig smtpe1.intersmtp.com. MX
Answer
The response has no answer records.
Authority
intersmtp.com. 86400 SOA ns0.bt.net. hostmaster.bt.net. 87 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0