Default is the value of the
<em>sendemail.thread</em> configuration value; if that is unspecified,
default to --thread.</p>
</div>
<div class="paragraph">
<p>It is up to the user to ensure that no In-Reply-To header already
exists when <em>git send-email</em> is asked to add it (especially note that
<em>git format-patch</em> can be configured to do the threading itself).
Failure to do so may not produce the expected result in the
recipient&#8217;s MUA.</p>
</div>
</dd>
</dl>
</div>
</div>
<di