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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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