Configure Incoming Filtering with Postfix

To restrict deliveries to your Postfix server from our filtering nodes and IP addresses, complete the below steps:

  1. Create the file /etc/postfix/access with the content:
    2. 185.201.16.200/24 OK
185.201.17.200/24 OK
185.201.18.200/24 OK
185.201.19.200/24 OK
  2. Execute the command:

    3. postmap /etc/postfix/access

  3. Either:
    1. Add the following to /etc/postfix/main.cf
      smtpd_client_restrictions = check_client_access hash:/etc/postfix/access, 
permit_mynetworks, reject

      2. OR

    2. If you already have smtpd_client_restrictions defined in /etc/postfix/main.cf, insert the following at the beginning of your definition and replace permit with reject at the end of definition:

      "check_client_access hash:/etc/postfix/access"

  4. Reload the Postfix configuration by executing the following command:

    5. sudo postfix reload

  5. Restart Postfix by executing the following command:

    6. /etc/init.d/postfix restart

Per domain setup

It's also possible with Postfix to configure the MTA to only allow connections from the Mail Assure servers for specific protected domains:

  1. Add the following to the main.cf
    2. smtpd_restriction_classes = mailassuremailassure = check_client_access hash:/etc/postfix/mailassure, reject
smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/protected_destinations, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
  2. Create the following file:
    3. /etc/postfix/mailassure
    1. Add the following content:
      2. 185.201.16.200/24 OK
185.201.17.200/24 OK
185.201.18.200/24 OK
185.201.19.200/24 OK
  3. Create the following file:

    4. /etc/postfix/protected_destinations

    1. Add the domains that you want to configure:

      2. demo-domain.invalid mailassure

  4. Postmap both files:

    5. postmap /etc/postfix/mailassure

    postmap /etc/postfix/protected_destinations

  5. Reload the Postfix configuration by executing the following command:

    6. sudo postfix reload

  6. Restart Postfix by executing the following command:

    7. /etc/init.d/postfix restart

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