testmxlookup — Look up mail relays for a domain
testmxlookup
[domain
...]
testmxlookup lists the names and IP addresses of mail
relays that receive mail for the domain
.
This is useful in diagnosing mail delivery problems.
testmxlookup sends a DNS MX query for the specified domain, followed by A/AAAA queries, if needed. testmxlookup lists the hostname and the IP address of every mail relay, and its MX priority.