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<section id="why-does-cyrus-reject-8-bit-characters-in-the-headers-of-my-messages">
<h1>Why does Cyrus reject 8-bit characters in the headers of my messages?<a class="headerlink" href="#why-does-cyrus-reject-8-bit-characters-in-the-headers-of-my-messages" title="Permalink to this heading"></a></h1>
<p>8-bit characters are not allowed in the headers of an <span class="target" id="index-0"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc822.html"><strong>RFC 822</strong></a>
message.</p>
<p>## Until release 3.0
We're not about to consider a patch to "fix" the problem of replacing
8-bit characters with 'X's that doesn't at least supply a default
character set and properly QP-encode the nonconforming header.</p>
<p>Another possibility is suggested by Chris Newman:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">The</span> <span class="n">correct</span> <span class="n">long</span> <span class="n">term</span> <span class="n">thing</span> <span class="n">to</span> <span class="n">do</span> <span class="ow">is</span> <span class="n">to</span> <span class="n">interpret</span> <span class="n">unlabelled</span> <span class="mi">8</span><span class="o">-</span><span class="n">bit</span> <span class="k">as</span>
<span class="n">UTF</span><span class="o">-</span><span class="mi">8</span> <span class="k">if</span> <span class="n">it</span> <span class="n">meets</span> <span class="n">the</span> <span class="n">UTF</span><span class="o">-</span><span class="mi">8</span> <span class="n">syntax</span><span class="p">,</span> <span class="ow">and</span> <span class="n">otherwise</span> <span class="n">give</span> <span class="n">it</span> <span class="n">the</span> <span class="s2">"unknown"</span>
<span class="n">charset</span> <span class="n">label</span> <span class="ow">and</span> <span class="n">downconvert</span> <span class="n">to</span> <span class="mi">7</span><span class="o">-</span><span class="n">bit</span> <span class="n">using</span> <span class="n">RFC</span> <span class="mf">2047.</span>
<span class="n">If</span> <span class="n">you</span> <span class="n">want</span> <span class="n">to</span> <span class="n">do</span>
<span class="n">something</span> <span class="n">really</span> <span class="n">fancy</span><span class="p">,</span> <span class="n">you</span> <span class="n">might</span> <span class="n">allow</span> <span class="n">a</span> <span class="n">mapping</span> <span class="kn">from</span> <span class="nn">the</span> <span class="n">hostname</span> <span class="ow">in</span>
<span class="n">the</span> <span class="n">envelope</span> <span class="kn">from</span> <span class="nn">address</span> <span class="n">to</span> <span class="n">a</span> <span class="n">default</span> <span class="mi">8</span><span class="o">-</span><span class="n">bit</span> <span class="n">charset</span> <span class="p">(</span><span class="n">Innosoft</span><span class="s1">'s MTA</span>
<span class="n">includes</span> <span class="n">an</span> <span class="n">equivalent</span> <span class="n">facility</span><span class="p">)</span> <span class="n">so</span> <span class="n">the</span> <span class="n">administrator</span> <span class="n">can</span> <span class="nb">set</span> <span class="n">up</span> <span class="n">private</span>
<span class="n">agreements</span> <span class="k">with</span> <span class="n">specific</span> <span class="n">hosts</span><span class="o">.</span>
</pre></div>
</div>
<p>## Release 3.0 and later
All the rationale for pre-3.0 8-bit character support still applies.</p>
<p>However, Cyrus now optionally <em>does</em> accept 8-bit characters in MIME header values
for internal processing, if they are valid UTF-8. For example, this allows Cyrus
to index 8-bit message header values for search or emit them on the JMAP or RSS
interfaces.</p>
<p>Please note that the original message header values are left as-is. That is,
Cyrus does not attempt to repair improperly encoded headers.</p>
<p>To enable this feature one must enable the <cite>rfc2047_utf8</cite> config option. This
causes Cyrus to interpret any high-bit character as UTF-8. Invalid UTF8
characters are internally processed with the UTF-8 replacement character.</p>
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