Mail Rule May Get Me Fired

Mail Rule May Get Me Fired: Managing Email Filters in Self-Hosted Environments

Welcome to this comprehensive guide on managing email filters in self-hosted environments, focusing on the popular open-source mail transfer agent (MTA) - Postfix. This article will help you understand why email filter management is crucial for your homelab or self-hosted infrastructure, and how to configure Postfix’s mail rule system effectively.

Prerequisites

To follow this guide, ensure you have:

1. A Linux system (Ubuntu 20.04 LTS, CentOS 8, etc.) with at least 2GB of RAM and 20GB of storage.
2. Postfix version 3.5 or higher installed.
3. Basic networking knowledge and firewall configuration skills.
4. Sufficient user permissions to modify system files and services.

Installation & Setup

Install Postfix using the following command:

sudo apt-get install postfix -y

Configure main settings in the /etc/postfix/main.cf file:

myhostname = your_server_name.example.com
myorigin = /etc/mailname
mydestination = localhost, your_server_name.example.com
relay_domains = example.com
inet_interfaces = all

Save and reload Postfix configuration:

sudo systemctl reload postfix

Configuration

Create a new mail filter in the /etc/postfix/virtual directory, for example:

your_junior@example.com: /var/mail/your_junior
filtered_emails: *

Next, create a transport map in the same directory:

filtered_emails: filter:myfilter

Now, create the filter script /etc/postfix/mysql-virtual-maps.cf:

user = postfix
password = your_database_password
dbname = your_database_name
select_field_separator = ','
query = SELECT recipient FROM mail_rules WHERE phrase REGEXP '(?i)^$1(.*)$'

Finally, create the /etc/postfix/mysql-virtual-maps.cf file for your database connection:

user = your_database_user
password = your_database_password
dbname = your_database_name
host = localhost
unix_socket = /var/run/mysqld/mysqld.sock

Usage & Operations

You can now create, edit, and delete email rules through your database (MySQL or PostgreSQL). Regularly monitor logs for performance tuning and troubleshooting purposes.

Troubleshooting

Common issues include incorrect regular expressions, missing tables in the database, and permission errors. Always verify your configurations, logs, and database connections before proceeding.

Conclusion

In this guide, we covered setting up and configuring email filters with Postfix in self-hosted environments using a MySQL or PostgreSQL backend. By following these steps, you can avoid situations like the one described in our title, where an overly specific mail rule might get someone fired. For advanced topics such as advanced filtering, external script integrations, and more, refer to Postfix’s official documentation.

Happy filtering! 📧💻