Dear HTF friends, I have been fighting with this problem for about 2 days now and i am still unable to solve it. If anyone has some advice it will be greatly appreciated. Setup : Multi server setup, ubuntu 16.0.4, nginx, ISPConfig 3.1.13p1 Problem : I recently added a new site (server2.hosting.com) and mailbox (mail.hosting.com) to one of my servers but somehow i am unable to connect to the imap/smtp mailbox for that domain. Other (older) domains work properly with TLS/Starttls but i can't seem to connect to the mail server's (mail.hosting.com) inbox for this specific one unless i disable all encryption else i get "please check your email and password and try again" from windows mail mobile. I checked the mail log and the only thing i could find is the connection session starts and an immediate logout right after.