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<section id="why-is-mail-being-rejected-with-no-mailbox-found-due-to-mixed-case-incoming-e-mail">
<h1>Why is mail being rejected with No Mailbox found due to MiXed CaSe incoming e-mail?<a class="headerlink" href="#why-is-mail-being-rejected-with-no-mailbox-found-due-to-mixed-case-incoming-e-mail" title="Permalink to this heading"></a></h1>
<p>If you are using a newer and standard compliant MTA to deliver mail to Cyrus IMAP's LMTP agent you may run into a problem where mail will be bounced and not delivered with errors like this in your maillog:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">Feb</span> <span class="mi">29</span> <span class="mi">10</span><span class="p">:</span><span class="mi">01</span><span class="p">:</span><span class="mi">02</span> <span class="n">myhost</span> <span class="n">lmtpunix</span><span class="p">[</span><span class="mi">12345</span><span class="p">]:</span> <span class="n">append_check</span><span class="p">()</span> <span class="n">of</span> <span class="s1">'MyDomain.tld!user.MyUser'</span> <span class="n">failed</span> <span class="p">(</span><span class="n">Mailbox</span> <span class="n">does</span> <span class="ow">not</span> <span class="n">exist</span><span class="p">)</span>
</pre></div>
</div>
<p>This is due to LMTP adhering to the RFC standards and the MTA adhering to the RFC standards of preserving the case in the e-mail address. so <a class="reference external" href="mailto:User%40MyDomain.tld">User<span>@</span>MyDomain<span>.</span>tld</a> is not the same as <a class="reference external" href="mailto:user%40mydomain.tld">user<span>@</span>mydomain<span>.</span>tld</a>. And this causes issues if with users who alter the case of their e-mail address when signing up for mailing lists, or sending e-mail.</p>
<p>However, all is not lost there is a solution. Cyrus IMAP has an option that can be added into the imapd.conf:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">lmtp_downcase_rcpt</span><span class="p">:</span> <span class="n">true</span>
</pre></div>
</div>
<p>Inserting that into your <a class="reference internal" href="../manpages/configs/imapd.conf.html#std-cyrusman-imapd.conf-5">imapd.conf(5)</a> and restarting cyrus imap will cause cyrus to "downcase" the e-mail address up to the recipient delimiter of +. The result will be this:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">User</span><span class="nd">@MyDomain</span><span class="o">.</span><span class="n">tld</span> <span class="o">-></span> <span class="n">user</span><span class="nd">@mydomain</span><span class="o">.</span><span class="n">tld</span>
<span class="n">user</span><span class="nd">@mydomain</span><span class="o">.</span><span class="n">tld</span> <span class="o">-></span> <span class="n">user</span><span class="nd">@mydomain</span><span class="o">.</span><span class="n">tld</span>
<span class="n">User</span><span class="o">+</span><span class="n">PostFolder</span><span class="nd">@MyDomain</span><span class="o">.</span><span class="n">tld</span> <span class="o">-></span> <span class="n">user</span><span class="o">+</span><span class="n">PostFolder</span><span class="nd">@MyDomain</span><span class="o">.</span><span class="n">tld</span>
</pre></div>
</div>
<p>Someone verify that the domain will actually be downcased when a + is used</p>
<p>Note that this option first appeared in Cyrus IMAP 2.1.14.</p>
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