I did not ask you to change your username, just the mail server address. And do not use SSL/TLS while you are still testing your connection.
Configure TB with :
User Name = firstname.lastname@example.org
(exactly as set up in ISPConfig, do *not* use the IP address here!)
Server Name = 192.168.1.9
Connection Security = NONE
Authentication Method = Normal Password
Use the same settings for incoming and outgoing server!
Then receive and send mail and post your Postfix log again.