Configuring Postfix to reject RCPT TO queries for local domain accounts involves two modification processes in an existing DDEI setup:

1. Modify main.cf configuration file to accept wildcards in the recipient_access table:
   1. Log in to the DDEI’s CLI using root account.

   2. Search for the parameter "unknown_local_recipient_reject_code" and change its value from 550 to 554:

      unknown_local_recipient_reject_code = 554

   3. Add the "show_user_unknown_table_name" at the bottom of the main.cf file and set its value to “no”.

   4. Configure smtpd_recipient_restrictions in main.cf:

      smtpd_recipient_restrictions = check_recipient_access pcre:/opt/trend/ddei/postfix/etc/postfix/recipient_access, permit_mynetworks, reject_unauth_destination

   5. Save the changes and exit out of the file.

2. Use regular expression in recipient_access file to define wildcard:

   1. Query the DDEI server’s hostname:

      # postconf myhostname
      myhostname = ddei-158.danielvm.com

   2. Create the /opt/trend/ddei/postfix/etc/postfix/recipient_access using the touch command:

      # cd /opt/trend/ddei/postfix/etc/postfix/
      # touch recipient_access

   3. Modify the recipient_access file to define the wildcard using the hostname identified in Step B6. For example:

      /.*@ddei-158.danielvm.com$/ REJECT Invalid Recipient

       

      Use a space to separate “REJECT” and “Invalid Recipient” messages.

       
   4. Save the changes and exit out of the file.

   5. Run postmap on the recipient_access file:

      # postmap /opt/trend/ddei/postfix/etc/postfix/recipient_access

   6. Restart the Postfix service.

      # service postfix restart

   7. Test via telnet email.

   On a test environment using the steps above, the test results looked like this: