Since upgrading from 3.8.3 to 3.8.4, the notification emails sent by PHP file scan display the HTML code as plain text because Content-Type is text/plain.
<html><head>File Scan results<title></title></head><body><h1>File Scan results</h1><hr/>
<h2>Overview</h2>
<p>
<strong>Total Files</strong>: 5127<br/>
<strong>Modified</strong>: 0<br/>
<strong>Added</strong>: 0<br/>
<strong>Suspicious</strong>: 0<br/>
</p>
<p>The PHP File Change Scanner has not detected and newly added, modified or suspicious files</p></body></html>