Am running the ZCS Version 8.0.5_GA_58399.FOSS Sep 10, 2013 server. I wish to block external email IDs from receiving the emails sent from my domain. I have checked a number of links but no solution seems in sight. Currently, if one use the Thunderbird or Outlook and if the mails are sent via SMTP port 25, the email is blocked. However, if we send the email using SSL Port 465 then the email is sent to the external email address. Please can someone shed some light on this.