RestrictPostfixRecipients

Revision as of 21:23, 3 November 2006 by Jdell (talk | contribs) (New page)

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Restrict Postfix Recipients

  • This will show how you can modify postfix to restrict who can send to certain addresses in your domain such as distribution lists like all@mydomain.com
  • These changes will most likely not persist between upgrades!
  • This method can be spoofed by forging the MAIL FROM: header (so mail appears to originate from within the domain), so it isn't foolproof, but it works for basic needs.

Steps

  • Create a 'permitted senders' list (as user zimbra) - This is your list of domains and/or users who can email your protected email addresses:
vi /opt/zimbra/postfix/conf/permitted_senders

[paste in contents below editing as required]

localhost               OK
mydomain.com            OK
zimbra.mydomain.com     OK
okuser@externaldom.com  OK
  • Create a 'protected recipients' list (as user zimbra) - This is your list of email addresses that may only receive email from 'permitted senders'
vi /opt/zimbra/postfix/conf/protected_recipients

[paste in contents below editing as required]

test-dist-list@mydomain.com         permitted_senders_list
protected-user@mydomain.com         permitted_senders_list 
  • Create a simple bash script to create postfix DB files (as user zimbra):
vi /opt/zimbra/postfix/conf/update_protected_recipients

[paste in contents below editing as required]

#!/bin/bash
echo "rebuild permitted_senders..."
postmap /opt/zimbra/postfix/conf/permitted_senders
echo "rebuild protected_recipients..."
postmap /opt/zimbra/postfix/conf/protected_recipients
  • You should see permitted_senders.db and protected_recipients.db in the directory now
  • Add necessary settings to /opt/zimbra/postfix/conf/main.cf
vi /opt/zimbra/postfix/conf/main.cf

[add these items to the file - note permitted_senders_list must match value in protected_recipients]

permitted_senders_list = check_sender_access hash:/opt/zimbra/postfix/conf/permitted_senders, reject
smtpd_restriction_classes = permitted_senders_list
  • Now add your new restriction to postfix_recipient_restrictions.cf
vi /opt/zimbra/conf/postfix_recipient_restrictions.cf

[paste this into the first line of the file above any other settings]

hash:/opt/zimbra/postfix/conf/protected_recipients
  • Reload postfix to activate settings:
postfix reload
  • Test your settings via telnet:
telnet zimbra.mydomain.com 25

You will see...

Trying 192.168.1.1...
Connected to zimbra.mydomain.com.
Escape character is '^]'.
220 zimbra.mydomain.com ESMTP Postfix
HELO test.com

You will see...

250 zimbra.mydomain.com
MAIL FROM: jdoe@test.com

You will see...

250 Ok
RCPT TO: test-dist-list@mydomain.com

You will see that it works!

554 <test-dist-list@mydomain.com>: Recipient address rejected: Access denied
QUIT
221 Bye
Connection closed by foreign host.
  • That's it. If you need to protect new distribution lists or emails, or add new senders, just edit and re-run the update script, then reload postfix.
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