testmxlookup -- Look up mail relays for a 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.
The error message "Hard error" indicates that the domain does not exist,
or does not have any mail relays. The error message "Soft error" indicates a
temporary error condition (usually a network failure of some sorts, or the
local DNS server is down).