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<title>smtpd-starttls-proxy: the qmail-remote-io internal program</title>
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<p>
<a href="index.html">smtpd-starttls-proxy</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
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<h1> The <tt>qmail-remote-io</tt> internal program </h1>
<p>
<tt>qmail-remote-io</tt> is a part of the SMTP client implemented by
<a href="qmail-remote.html">qmail-remote</a>. It manages the entirety
of the SMTP transaction except <tt>EHLO</tt> and <tt>STARTTLS</tt>.
</p>
<p>
<tt>qmail-remote-io</tt> is not meant to be invoked directly. It is
meant to be executed into by <a href="qmail-remote.html">qmail-remote</a>.
</p>
<h2 id="details"> Internal details </h2>
<ul>
<li> <a href="qmail-remote.html">qmail-remote</a> does the job of finding a
suitable SMTP server and connecting to it, saying <tt>EHLO</tt> and, if the user
has defined a <tt>control/trustanchors</tt> file and the server supports it,
<tt>STARTTLS</tt>. </li>
<li> If the connection is not encrypted,
<a href="qmail-remote.html">qmail-remote</a> execs <tt>qmail-remote-io</tt>
immediately, and <tt>qmail-remote-io</tt> proceeds with all the rest of the
SMTP transaction. </li>
<li> If the connection is encrypted,
<a href="qmail-remote.html">qmail-remote</a> execs
<tt><a href="//skarnet.org/software/s6-networking/s6-tlsc.html">s6-tlsc</a>
qmail-remote-io</tt>, instead, so any further exchange with the SMTP server
is protected by TLS. </li>
<li> <tt>qmail-remote-io</tt> does the same job in either case: it speaks
plaintext SMTP. </li>
</ul>
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