As of Firefox version 3.0.7 some text only emails will not display in the popup "read email" window on the Advanced Interface. To resolve the issue you have two options:

Option 1

If you have access to our Trac you can download the fixed version of the relevant file from http://dev.atmail.com/tracphp/browser/trunk/webmail/lang/html/xul/readmail-frame.html?rev=1846&format=txt

Save this file to html/lang/xul/readmail-frame.html and from your Atmail web-root you will then need to run:

php lang.php english lang/languages/english/english.lang

Of cause replace "english" with your required language if required

Option 2

Edit html/{your-lang}/xul/readmail-frame.html:

Add this into the body tag: onload="msgwinint()"

and near the bottom of the file replace:

msgwin.document.open();
msgwin.document.write('' + document.getElementById('atmailmsg').innerHTML);
msgwin.document.close();

with:

function msgwinint() {
msgwin.document.open();
msgwin.document.write('' + document.getElementById('atmailmsg').innerHTML);
msgwin.document.close();
}