I also have problems activating E-Mail.
I'm using an IMAP account using the settings my provider gave me: port 143 and TLS/STARTTLS. To my understanding I should enter the e-mail server's hostname, check SSL in osTicket's interface and enter port and account, check "enable".
When I submit the new settings I get a 324 error message from my browser. Any suggestions to get this to work?