In our older postfix mail server we could see the connections that were dropped using RBL check lists, is this possible in Zimbra ?
Making Postfix daemon programs more verbose
Append one or more "-v" options to selected daemon definitions in /etc/postfix/master.cf and type "postfix reload". This will cause a lot of activity to be logged to the syslog daemon. For example, to make the Postfix SMTP server process more verbose:
smtp inet n - n - - smtpd -v
Will this work ??