Provided by: courier-base_1.0.6-1_amd64 bug

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)
           http://www.courier-mta.org/courier.html

        2. RFC 1035
           https://www.ietf.org/rfc/rfc1035.txt