This site browses the 4927 emails from Really Good Emails to count the use of certain HTML and CSS features. The numbers on this page indicate the percentage of HTML emails that use the corresponding HTML or CSS feature at least once.
Data is updated every month.

HTML Percentage
<tr>
96.59022%
<td>
96.26548%
<table>
96.00162%
<a>
94.68236%
<img>
90.0345%
<div>
85.75198%
<br>
82.22042%
<span>
77.877%
<tbody>
66.18632%
<style>
65.57743%
<head>
58.61579%
<meta>
58.35194%
<body>
56.22082%
<p>
54.08971%
<title>
50.11163%
<center>
43.45443%
<html>
36.02598%
<strong>
34.92998%
<h1>
19.05825%
<xml>
16.82565%
<o:pixelsperinch>
16.82565%
<o:officedocumentsettings>
16.64299%
<o:allowpng>
16.60239%
<em>
16.05439%
<h2>
15.4861%
<link>
14.87721%
<b>
12.60402%
<th>
12.1778%
<v:textbox>
11.85305%
<v:rect>
11.69068%
<v:fill>
10.39172%
<h3>
10.29024%
<hr>
10.10757%
<font>
9.86401%
<w:anchorlock>
7.89527%
<li>
7.08342%
<ul>
6.6572%
<v:roundrect>
6.35275%
<u>
5.5206%
<h4>
4.60727%
<i>
4.22164%
<sup>
3.16623%
<input>
2.61823%
<label>
2.49645%
<section>
2.41526%
<v:image>
1.86726%
<h5>
1.48163%
<small>
1.46134%
<thead>
1.13659%
<v:background>
1.13659%
<blockquote>
0.97422%
<ol>
0.95393%
<h6>
0.93363%
<source>
0.93363%
<nobr>
0.83215%
<custom>
0.81185%
<form>
0.71037%
<footer>
0.66978%
<picture>
0.66978%
<header>
0.58859%
<map>
0.50741%
<area>
0.48711%
<strike>
0.40593%
<pre>
0.40593%
<video>
0.38563%
<media_query_styles>
0.30444%
<o:p>
0.28415%
<button>
0.26385%
<singleline>
0.26385%
<main>
0.24356%
<code>
0.20296%
<no>
0.20296%
<address>
0.20296%
<v:shape>
0.18267%
<unsubscribe>
0.18267%
<nav>
0.16237%
<s>
0.16237%
<figure>
0.16237%
<article>
0.14207%
<wbr>
0.12178%
<time>
0.12178%
<base>
0.10148%
<v:shapetype>
0.10148%
<ins>
0.10148%
<sub>
0.10148%
<noscript>
0.10148%
<figcaption>
0.08119%
<left>
0.08119%
<raw>
0.08119%
<tfoot>
0.08119%
<col>
0.08119%
<g>
0.08119%
<multiline>
0.08119%
<column>
0.08119%
<colgroup>
0.06089%
<option>
0.06089%
<select>
0.06089%
<bdo>
0.06089%
<audio>
0.06089%
<a:textbox>
0.06089%
<doctype>
0.06089%
<o:allowjpg>
0.04059%
<cite>
0.04059%
<caption>
0.04059%
<i18n-string>
0.04059%
<selector>
0.04059%
<a:roundrect>
0.04059%
<field>
0.0203%
<bodycopy>
0.0203%
<webversion>
0.0203%
<tr_>
0.0203%
<abbr>
0.0203%
<v:oval>
0.0203%
<divre>
0.0203%
<eloqua>
0.0203%
<pstyle="text-align:>
0.0203%
<thea>
0.0203%
<dviv>
0.0203%
<cq:include>
0.0203%
<layout>
0.0203%
<svg>
0.0203%
<rect>
0.0203%
<circle>
0.0203%
<spanonlin>
0.0203%
<script>
0.0203%
<big>
0.0203%
<amp-anim>
0.0203%
<i-amphtml-sizer>
0.0203%
<amp-img>
0.0203%
<amp-accordion>
0.0203%
<xml:namespace>
0.0203%
<ampscript>
0.0203%
<repeater>
0.0203%
<choice>
0.0203%
<f>
0.0203%
<aside>
0.0203%
<textarea>
0.0203%
<mj-text>
0.0203%
<style-type="text/css">
0.0203%
<module>
0.0203%
<modulezone>
0.0203%
<editable>
0.0203%
<canvas>
0.0203%
<intro-directions>
0.0203%
<foo>
0.0203%
<mj-raw>
0.0203%
<assign>
0.0203%
<emsp>
0.0203%
<v:shadow>
0.0203%
<tablewidth="100%"border="0"cellspacing="0"cellpadding="0"background="">
0.0203%
<o:officedocumensettings>
0.0203%
<del>
0.0203%
<ptdashes>
0.0203%
<noplaintext>
0.0203%
<legend>
0.0203%
<iframe>
0.0203%
<fieldset>
0.0203%
<en>
0.0203%
<span.bold>
0.0203%
<text>
0.0203%