<p>I ran the following Overpass query on an April 2019 planet:</p>
<pre><code>[out:csv(::count, ::"count:nodes", ::"count:ways", ::"count:relations")];
nwr["email"];out count;
nwr["email"~"@"];out count;
nwr["email"~";"];out count;
nwr["contact:email"];out count;
nwr["contact:email"~"@"];out count;
nwr["contact:email"~";"];out count;
</code></pre>
<table>
<thead>
<tr>
<th>Test case</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a></th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:nodes</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:ways</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:relations</th>
</tr>
</thead>
<tbody>
<tr>
<td>All email</td>
<td>321586</td>
<td>223544</td>
<td>93158</td>
<td>4884</td>
</tr>
<tr>
<td>@ in email</td>
<td>320877</td>
<td>223116</td>
<td>92896</td>
<td>4865</td>
</tr>
<tr>
<td>; in email</td>
<td>939</td>
<td>754</td>
<td>167</td>
<td>18</td>
</tr>
</tbody>
</table>
<table>
<thead>
<tr>
<th>Test case</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a></th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:nodes</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:ways</th>
<th><a class="user-mention" data-hovercard-type="organization" data-hovercard-url="/orgs/count/hovercard" href="https://github.com/count">@count</a>:relations</th>
</tr>
</thead>
<tbody>
<tr>
<td>All contact:email</td>
<td>106861</td>
<td>72930</td>
<td>32617</td>
<td>1314</td>
</tr>
<tr>
<td>@ in contact:email</td>
<td>106687</td>
<td>72805</td>
<td>32572</td>
<td>1310</td>
</tr>
<tr>
<td>; in contact:email</td>
<td>414</td>
<td>318</td>
<td>84</td>
<td>12</td>
</tr>
</tbody>
</table>
<p>My conclusion would be  that semicolons in email addresses are a fairly niche requirement as they don't even affect 0,5% of all objects. I would just ignore those, it's not worth the effort.</p>

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