postfix/smtpd[9211]: lost connection after UNKNOWN from localhost[127.0.0.1]

Hi there,

i set up an MTA with your how-to.
In addition to that i set up also greylisting, always with your how to, and a webmail with roundcube.

All works fine but when i try to send a mail with the webmail it fails, and in the logs i see the error shown in subject.
Could you please help me?

 

Are there any other errors in your mail log?
What's the output of

Code:

netstat -tap

?