Interesting. Reading through your stack trace, it looks like somehow you're looking up a NULL module. What version of vTiger are you running? I'd take a look at the code around<div><br></div><div><span style>#4</span><br style>
<span style>/var/www/vtigercrm/modules/</span><span style>MailManager/src/controllers/</span><span style>MailController.php(142):</span><br style><span style>getMergedDescription('<p>??bl;</span><span style>ah</p>?', '1', NULL)</span><br style>
</div><div><font color="#222222" face="arial, sans-serif"><br></font></div><div><font color="#222222" face="arial, sans-serif">and try to figure out where that NULL is coming from.</font></div>