I recently upgraded one SmarterMail from v15 yo v16 and it worked fine for few days. Suddenly today it wont let me login and if I try to reset the admin password using the mailConfig.xml method as per portal.smartertools.com/kb/a2739/reset-administrator-username-and-password.aspx it still wont let me login.

 

I have tried to backup mailConfig.xml and tried a fresh install and the issue still remains same. Whatever admin password I configure it wont let me login.