this is a limitation to CSS support in email clients.
Not all CSS standards are supported in email clients, the overflow property is one that is not.
you would need to use PHP to force wordwrap on the string.
it looks like the name of the form element in question is comments, add the following code at line 1 to force word wrap at 50 characters:
<?php if(isset($_POST['comments']) && $_POST['comments'] != "") $_POST['comments'] = wordwrap($_POST['comments'],50,"<br>",true); ?>