We have had mandrill set up for use with Xenforo for a while now and had no problem, but after last minor Xenforo version update, our emails stopped being sent on everything except Conversations. We do not have encryption set on the SMTP settings We are seeing the PHP: Zend_Mail_Protocol_Exception: Email to _______@__________.com failed: Incorrect authentication data - library/Zend/Mail/Protocol/Abstract.php:431 message come up on all mails, except the Conversation ones. The Conversation emails are getting sent correctly somehow. We have checked throughly the mandrill details and tried using ssl and tls with varying ports. The fact that Conversation emails send properly through mandrill but anything else fails makes us believe the problem may be with Xenforo Has anyone else seen this recently? Any ideas on how to fix?