Add SPF validation to Postfix

Add SPF validation to Postfix

Installing and configuring postfix-policyd-spf-python on CentOS 6.11 While CentOS 6.11 is an older release, you can still install and configure postfix-policyd-spf-python to enhance your Postfix mail server’s SPF checking capabilities.

Important: Before you begin, ensure you have the EPEL repository enabled on your CentOS 6.11 system, as postfix-policyd-spf-python may be available in this repository.
Steps to install and configure:

Install required packages:

sudo yum install pypolicyd-spf

If pypolicyd-spf is not available, you might need to install epel-release first. If pypolicyd-spf is still not found, you may need to look for python-policyd-spf or explore other options like compiling from source, which might be more complex for an older system like CentOS 6.11.

Add a user for policyd-spf:

sudo adduser policyd-spf --user-group --no-create-home -s /bin/false

This creates a dedicated user for running the SPF policy daemon.
Configure Postfix master.cf:

Open the Postfix master process configuration file:

sudo nano /etc/postfix/master.cf

Add the following lines at the end of the file to configure Postfix to start the SPF policy daemon:

policyd-spf  unix  -  n  n  -  0  spawnuser=policyd-spf  argv=/usr/local/bin/policyd-spf

Note: Make sure the path to policyd-spf is correct for your installation.

Configure Postfix main.cf:

Open the Postfix main configuration file:

sudo nano /etc/postfix/main.cf

Add the following lines at the end of the file to enable SPF checking and set the policy agent timeout:

smtpd_recipient_restrictions =
  ...
  reject_unauth_destination,
  check_policy_service unix:private/policyd-spf

policyd-spf_time_limit = 3600

Important: Ensure check_policy_service unix:private/policyd-spf is listed AFTER reject_unauth_destination to prevent your system from becoming an open relay.

Restart Postfix:

sudo service postfix restart

Verify and test:

Check your mail logs (usually /var/log/maillog) to see if policyd-spf is running and processing incoming mail. Test the policy daemon manually by running policyd-spf with sample input as described in the policyd-spf.conf(5) documentation. Send test emails from various sources to ensure SPF checks are being performed correctly.

Additional Notes:

• Configuration file: You can customize policyd-spf’s behavior by modifying the configuration file, typically located at /etc/python-policyd-spf/policyd-spf.conf.
• Debugging: Increase the debugLevel in the configuration file to get more detailed logging information.
• SPF Records: Ensure you have correctly configured SPF records for your domain in your DNS.
• DNS Caching: Using a local caching DNS resolver is recommended for optimal performance.
• Alternative versions: If you encounter issues with the Python version on CentOS 6.11, you may need to install a newer Python version or explore alternative SPF policy agents like postfix-policyd-spf-perl.

By following these steps, you should be able to successfully install and configure postfix-policyd-spf-python on your CentOS 6.11 system and enhance your mail server’s security by utilizing SPF validation