I tested this whith a virgin install.
But anyway I was checking for gdpr compliance, etc and I noticed a issue in the footer.
Which seems to be in the language files mailer.php
In particular the top 4 keys in the raw zip file:
$ubbt_lang['EMAIL_HEADER_TEXT'] = "{$config['COMMUNITY_TITLE']}<br>----------------------------------<br>";
$ubbt_lang['EMAIL_HEADER_HTML'] = "{$config['COMMUNITY_TITLE']}";
$ubbt_lang['EMAIL_FOOTER_TEXT'] = "This email was auto-generated. Please do not reply.<br><br>Manage your email preferences:<br>{$config['FULL_URL']}/ubbthreads.php?ubb=editdisplay<br><br>Update your forum profile:<br>{$config['FULL_URL']}/ubbthreads.php?ubb=editbasic<br><br>";
$ubbt_lang['EMAIL_FOOTER_HTML'] = "This email was sent by <a href=\"{$config['HOMEPAGE_URL']}\">{$config['HOMEPAGE_TITLE']}</a>.<br>To control which emails we send you, <a href=\"{$config['FULL_URL']}/ubbthreads.php?ubb=editdisplay\">update your email preferences</a>.";
But after a net new install I get in the language file in the cp:
Ca't seem to copy paste the key with the text so will manually enter it
EMAIL_HEADER_TEXT <br>----------------------------------<br>
EMAIL_HEADER_HTML
EMAIL_FOOTER_TEXT This email was auto-generated. Please do not reply.<br><br>Manage your email preferences:<br>/ubbthreads.php?ubb=editdisplay<br><br>Update your forum profile:<br>/ubbthreads.php?ubb=editbasic<br><br>
EMAIL_FOOTER_HTML This email was sent by <a href=""></a>.<br>To control which emails we send you, <a href="/ubbthreads.php?ubb=editdisplay">update your email preferences</a>.
So what happens when you send a email from the site what is displayed in the footer is first no community title and the link to change your preferences is a relative url which will not redirect the user.
Attached two images of the email