testmxlookup(1)
NAME
testmxlookup - Look up mail relays for a domain
SYNOPSIS
testmxlookup [@ip-address] [--dnssec] [--udpsize n] {domain}
DESCRIPTION
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.
DIAGNOSTICS
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).
OPTIONS
@ip-address
Specify the DNS server's IP address, where to send the DNS query
to, overriding the default DNS server addresses read from
/etc/resolv.conf.
"ip-address" must be a literal, numeric, IP address.
--dnssec
Enable the DNSSEC extension. If the DNS server has DNSSEC enabled,
and the specified domain's DNS records are signed, the list of IP
addresses is suffixed by "(DNSSEC)", indicating a signed response.
This is a diagnostic option. Older DNS servers may respond with an
error, to a DNSSEC query.
--udpsize n
Specify that n is the largest UDP packet size that the DNS server
may send. This option is only valid together with "--dnssec". If
"--dnssec" always returns an error, try "--udpsize 512" (the
default setting is 1280 bytes, which is adequate for Ethernet, but
other kinds of networks may impose lower limits).
SEE ALSO
courier(8)[1], RFC 1035[2].
AUTHOR
Sam Varshavchik
Author
NOTES
1. courier(8)
[set $man.base.url.for.relative.links]/courier.html
2. RFC 1035
http://www.rfc-editor.org/rfc/rfc1035.txt
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