93.102.92.134.rev.optimus.pt has no MX records.
Question and response
Question
dig 93.102.92.134.rev.optimus.pt. MX
Answer
The response has no answer records.
Authority
optimus.pt. 1800 SOA kianchau.ns.cloudflare.com. dns.cloudflare.com. 2396961936 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0