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--></head><body><div class="refentry"><a id="idm247891451024" shape="rect"> </a><div class="titlepage"/><div class="refnamediv"><h2>Name</h2><p>testmxlookup — Look up mail relays for a domain</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">testmxlookup</code> [@<em class="replaceable"><code>ip-address</code></em>] [--dnssec] [--udpsize <em class="replaceable"><code>n</code></em>] {<em class="replaceable"><code>domain</code></em>}</p></div></div><div class="refsect1"><a id="idm247891351536" shape="rect"> </a><h2>DESCRIPTION</h2><p>
<span class="command"><strong>testmxlookup</strong></span> lists the names and IP addresses of mail
relays that receive mail for the <em class="replaceable"><code>domain</code></em>.
This is useful in diagnosing mail delivery problems.</p><p>
<span class="command"><strong>testmxlookup</strong></span> sends a DNS MX query for the specified domain,
followed by A/AAAA queries, if needed.
<span class="command"><strong>testmxlookup</strong></span> lists the
hostname and the IP address of every mail relay, and its MX priority.</p><div class="refsect2"><a id="idm247891347520" shape="rect"> </a><h3>DIAGNOSTICS</h3><p>
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).</p></div><div class="refsect2"><a id="idm247891346016" shape="rect"> </a><h3>OPTIONS</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">@ip-address</code></span></dt><dd><p>
Specify the DNS server's IP address, where to send the DNS
query to, overriding the default DNS server addresses read from
<code class="filename">/etc/resolv.conf</code>.
</p><p>
<span class="quote">“<span class="quote">ip-address</span>”</span> must be a literal, numeric,
IP address.
</p></dd><dt><span class="term"><code class="literal">--dnssec</code></span></dt><dd><p>
Enable the <code class="literal">DNSSEC</code> extension. If the DNS
server has <code class="literal">DNSSEC</code> enabled, and the
specified domain's DNS records are signed, the list of
IP addresses is suffixed by <span class="quote">“<span class="quote">(DNSSEC)</span>”</span>, indicating
a signed response.
</p><p>
This is a diagnostic option. Older DNS servers may respond with
an error, to a DNSSEC query.
</p></dd><dt><span class="term"><code class="literal">--udpsize</code> <em class="replaceable"><code>n</code></em></span></dt><dd><p>
Specify that <em class="replaceable"><code>n</code></em> is the largest
<acronym class="acronym">UDP</acronym> packet size that the DNS server may
send. This option is only valid together with
<span class="quote">“<span class="quote">--dnssec</span>”</span>.
If <span class="quote">“<span class="quote">--dnssec</span>”</span> always returns an error, try
<span class="quote">“<span class="quote">--udpsize 512</span>”</span> (the default setting is 1280
bytes, which is adequate for Ethernet, but other kinds of
networks may impose lower limits).
</p></dd></dl></div></div></div><div class="refsect1"><a id="idm247891436032" shape="rect"> </a><h2>SEE ALSO</h2><p>
<a class="ulink" href="courier.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">courier</span>(8)</span></a>,
<a class="ulink" href="http://www.rfc-editor.org/rfc/rfc1035.txt" target="_top" shape="rect">RFC 1035</a>.</p></div></div></body></html>
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