Linux Tactic

Enhancing Email Security: Setting Up DKIM and DMARC for Your Server

Rspamd is an open-source spam filtering system that helps prevent unwanted emails from reaching your inbox. In this article, we will outline the main steps required to set up and configure Rspamd spam filtering system on your email server.

This guide will cover the installation, configuration, and integration of Rspamd with your mail server, as well as creating DKIM and DMARC DNS records.

Prerequisites

Before we get started, there are some prerequisites you will need to fulfill. Firstly, you will need to log in as a user with sudo privileges.

This will allow you to install the required software packages and configure the system settings. Additionally, you will need to install Redis, which is a high-performance in-memory key-value database.

Redis will be used as a backend storage solution for Rspamd. Finally, you need to install Unbound, a validating, recursive, and caching DNS resolver that Rspamd uses for DNS queries.

Installation and Configuration of Rspamd

The first step is to install Rspamd and configure it on your system. Here are the steps to follow:

Step 1: Add the Rspamd repo and install it using the below command:

sudo apt-get install rspamd

Step 2: Once the installation is finished, run the following command to check if it’s working:

sudo systemctl status rspamd

Step 3: Configure Rspamd according to your requirements. The main configuration file for Rspamd is located in /etc/rspamd/rspamd.conf.

You can make changes to this file based on your needs. For example, you can enable the modules you need or configure which ports Rspamd listens on.

It is recommended that you read the documentation to understand the configuration options available.

Integration of Rspamd with Mail Server

Rspamd can be integrated with a mail server to filter out spam emails. Here are some steps to follow to integrate Rspamd:

Step 1: Make sure your mail server supports the LMTP or SMTP protocol.

Step 2: Configure your mail server to send all incoming emails to Rspamd for spam filtering. The configuration of this depends on the mail server you are using.

Here is an example of how to configure postfix:

In the /etc/postfix/main.cf file, add the following line:

smtpd_milters = inet:127.0.0.1:11332

Step 3: Restart your mail server to apply the changes.

Creating DKIM and DMARC DNS Records

DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting, and Conformance) are two mechanisms that help to prevent email fraud and phishing. Here are the steps to create DKIM and DMARC DNS records:

Step 1: Generate a DKIM key pair using the openssl command:

openssl genrsa -out private.key 2048

openssl rsa -in private.key -out public.key -pubout -outform PEM

Step 2: Add the public key to your DNS server as a TXT record.

For example, if your domain is example.com, the TXT record should look like this:

default._domainkey IN TXT “v=DKIM1;k=rsa;p=

Step 3: Create a DMARC policy to specify what should happen if a message fails authentication. You can do this by adding a TXT record to your DNS server:

_dmarc IN TXT “v=DMARC1; p=quarantine; pct=100; rua=mailto:[email protected]

Conclusion

We hope this guide has given you a better understanding of how to set up and configure Rspamd spam filtering system. It is an essential tool for protecting your email server from spam and unwanted emails.

By following the steps outlined in this guide, you will be able to set up a robust spam filtering system that is tailored to your needs. Remember to test your configuration thoroughly to confirm that Rspamd is working correctly.

In continuation of the previous article, we will now cover how to install and configure Rspamd, as well as setting Redis as a backend for Rspamd statistics. We will also discuss how to configure Nginx as a reverse proxy to Rspamd web interface.

Installation and Configuration of Rspamd

Adding Rspamd Repository and Installing Necessary Packages

The first step to install Rspamd is to add the Rspamd repository to your system. To do this, you need to create a file named “rspamd.list” in the /etc/apt/sources.list.d/ directory and add the repository’s URL to the file.

Here are the steps to follow:

Step 1: Open the terminal and type the following command:

sudo nano /etc/apt/sources.list.d/rspamd.list

Step 2: Add the following line to the file:

deb http://packages.rspamd.com/ubuntu focal main

Step 3: Save and exit the file. Next, you need to install the necessary packages for Rspamd to function correctly.

You can do this by running the command:

sudo apt-get update &&

sudo apt-get install rspamd

Configuring Rspamd

Once you have installed Rspamd, you need to configure it to meet your needs. The main configuration file for Rspamd is located in /etc/rspamd/rspamd.conf.

Here are some important configuration options you should consider:

– Enable or disable specific modules according to your needs. For example, you can enable the DKIM module if you want to verify DKIM signatures on incoming emails.

– Configure which ports Rspamd listens on. By default, Rspamd listens on port 11333 for its worker processes and port 11334 for its control interface.

You can change these ports in the configuration file. – Adjust the logging options to suit your requirements.

You can configure Rspamd to log different levels of information, from simple error messages to more detailed debug information. – Define your spam filtering rules.

Rspamd uses a ruleset system, which allows you to define conditions that incoming emails must meet to be considered spam.

Setting Redis as a Backend for Rspamd Statistics

Rspamd can generate statistics on the spam filtering performance, which can be useful for analyzing and improving your spam filtering rules. To store these statistics, you can use Redis, which is a high-performance, in-memory key-value database.

Here are the steps to configure Redis as a backend for Rspamd statistics:

Step 1: Install Redis if you haven’t already done so. You can do this by running the command:

sudo apt-get install redis

Step 2: Open the /etc/rspamd/local.d/redis.conf file and configure the following parameters:

– Set the “enable” parameter to “true” to enable Redis support. – Set the “type” parameter to “redis” to specify that you want to use Redis as the backend.

– Set the “host” parameter to the IP address or hostname of the Redis server. – Set the “port” parameter to the port number used by Redis (usually 6379).

Step 3: Save and exit the file, then restart the Rspamd service to apply the changes:

sudo systemctl restart rspamd

Configuring Nginx

Adding Location Directive to Nginx Configuration File

Before we can configure Nginx as a reverse proxy for Rspamd web interface, we need to add a location directive to the Nginx configuration file. The location directive specifies the URL path that should be mapped to a specific location in the file system.

Here are the steps to add the location directive:

Step 1: Open the Nginx configuration file using the following command:

sudo nano /etc/nginx/sites-available/default

Step 2: Find the “server” section and add the following location directive:

location /rspamd {

proxy_pass http://localhost:11334;

proxy_http_version 1.1;

proxy_set_header Upgrade $http_upgrade;

proxy_set_header Connection $connection_upgrade;

proxy_set_header Host $host;

proxy_set_header X-Real-IP $remote_addr;

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

}

Step 3: Save and exit the file, then restart the Nginx service to apply the changes:

sudo systemctl restart nginx

Configuring Nginx as a Reverse Proxy to Rspamd Web Interface

Now that we have added the required location directive to the Nginx configuration file, we can configure Nginx as a reverse proxy to the Rspamd web interface. The Rspamd web interface provides a graphical user interface for managing the spam filtering rules and viewing statistics.

Here are the steps to configure Nginx as a reverse proxy:

Step 1: Install the Nginx package if you haven’t already done so:

sudo apt-get install nginx

Step 2: Open the Nginx configuration file using the following command:

sudo nano /etc/nginx/sites-available/default

Step 3: Find the “server” section and add the following location directive under the existing “location /” block:

location /dashboard {

proxy_pass http://localhost:8080;

}

Note: Replace “localhost” with the IP address or hostname of the Rspamd server if you are running Nginx on a separate server. Step 4: Save and exit the file, then restart the Nginx service to apply the changes:

sudo systemctl restart nginx

Conclusion

In this article, we have covered how to install and configure Rspamd, including setting Redis as a backend for Rspamd statistics. We have also discussed how to configure Nginx to act as a reverse proxy to the Rspamd web interface.

By following the steps provided, you should be able to set up a powerful spam filtering system that suits your needs. Remember to test your configuration carefully to ensure that everything is working correctly.

In this article, we will cover how to configure Postfix and Dovecot to work together with Rspamd. Postfix and Dovecot are two of the most commonly used mail servers, and integrating them with Rspamd can significantly improve your mail server’s spam filtering capability.

Configuring Postfix

Configuring Postfix to Use Rspamd Milter

Postfix supports the use of milters, which are applications that can filter incoming and outgoing emails. Rspamd provides a milter that can be used with Postfix to filter out spam emails.

Here are the steps to configure Postfix to use Rspamd milter:

Step 1: Install the milter library for Postfix by running the following command:

sudo apt-get install postfix-policyd-spf-python postfix-pcre postfix-lmdb libmilter-dev

Step 2: Open the /etc/postfix/main.cf file and add the following lines:

smtpd_milters = unix:/var/run/rspamd/worker-proxy

non_smtpd_milters = unix:/var/run/rspamd/worker-proxy

milter_protocol = 6

milter_mail_macros = i {mail_addr} {client_addr} {client_name} {auth_authen}

milter_default_action = accept

Step 3: Save and exit the file, then restart the Postfix service to apply the changes:

sudo systemctl restart postfix

Configuring Dovecot

Installing and Configuring Sieve Filtering Module for Dovecot

Dovecot includes a sieve filtering module that can be used to automatically filter incoming emails based on specific conditions. This module needs to be installed and configured to work with Rspamd.

Here are the steps to do this:

Step 1: Install the Dovecot sieve filtering module and the Rspamd sieve plugin:

sudo apt-get install dovecot-sieve dovecot-managesieved rspamd-sieve

Step 2: Open the /etc/dovecot/conf.d/20-lmtp.conf file and add the following line:

protocol lmtp {

postmaster_address = [email protected]

mail_plugins = sieve

# See /usr/share/doc/dovecot-core/dovecot/example.conf for a commented example file. # Sieve plugin

sieve = file:~/sieve;active=~/.dovecot.sieve

sieve_dir = ~/sieve

sieve_global_dir = /var/lib/dovecot/sieve/

sieve_extensions = +timed-events +spamtest

}

The above configuration sets the sieve filter location, enables the sieve plugin, and specifies the sieve extension.

Step 3: Save and exit the file, then create the filter file by running the following commands:

mkdir -p ~/.dovecot.sieve

nano ~/.dovecot.sieve/default.sieve

Add the following initial configuration line:

require [“fileinto”, “reject”, “infix”, “relational”, “comparator-i;ascii-numeric”, “spamtest”];

Step 4: Save and exit the file, then restart the Dovecot service:

sudo systemctl restart dovecot

Integrating Dovecot with Rspamd

Once Dovecot is set up to use the sieve filtering module, we can integrate it with Rspamd so that the spam filtering rules created in Rspamd are applied to the filtered email. Here are the steps to integrate Dovecot with Rspamd:

Step 1: Open the /etc/dovecot/conf.d/90-plugin.conf file and add the following lines:

plugin {

# Spamassassin

sieve_before = /usr/lib/dovecot/sieve-antispam.sieve

# Rspamd

sieve_before = /usr/lib/dovecot/sieve-rspamd.sieve

}

Step 2: Save and exit the file, then create the rspamd sieve file by running the following command:

nano /usr/lib/dovecot/sieve-rspamd.sieve

Add the following lines:

require “fileinto”;

if header :contains “X-Spam-Flag” “YES” {

fileinto “Junk”;

stop;

}

Step 3: Save and exit the file, then restart the Dovecot service:

sudo systemctl restart dovecot

The above configuration sets Dovecot to use the sieve-antispam.sieve file first, followed by the sieve-rspamd.sieve file. The sieve-rspamd.sieve file checks the email headers for the X-Spam-Flag header, which Rspamd sets for spam emails.

If the header is present, the email is filed into the Junk folder.

Conclusion

In this article, we have covered the steps to configure Postfix and Dovecot to work together with Rspamd. By integrating Rspamd with your mail server, you can significantly improve your spam filtering capability, ultimately improving your email service’s security and reliability.

Remember to test your configuration carefully to ensure that everything is working correctly. In this article, we will cover how to create DKIM keys and DMARC records to enhance the security and authenticity of your email server.

DKIM (DomainKeys Identified Mail) allows the recipient to verify that an email comes from a trusted source, while DMARC (Domain-based Message Authentication, Reporting, and Conformance) helps prevent email spoofing and phishing attacks. By implementing DKIM and DMARC, you can improve the deliverability and trustworthiness of your emails.

Creating DKIM Keys

Generating DKIM Keypair using Rspamadm Utility

Rspamd provides a utility called rspamadm that can be used to generate DKIM key pairs. Here are the steps to generate a DKIM key pair using rspamadm:

Step 1: Open the terminal and run the following command to generate a DKIM key pair:

rspamadm dkim_keygen -s example.com -d /etc/rspamd/dkim/

Replace “example.com” with your own domain name.

The -d option specifies the destination directory for the DKIM key files. Step 2: The command will generate a private key file and a corresponding public key file in the specified directory.

Setting Rspamd to Look for DKIM Key and Enabling DKIM Signing for Alias Sender Addresses

Once you have generated the DKIM key pair, you need to configure Rspamd to use the key for signing outgoing emails. Here’s how:

Step 1: Open the /etc/rspamd/local.d/dkim_signing.conf file and add the following lines:

“domain” {

path = “/etc/rspamd/dkim/example.com.key”;

selector = “default”;

canonicalization = “relaxed/relaxed”;

headers = “from:to:cc:subject:date:message-id:mime-version:content-type:content-transfer-encoding:resent-to:resent-cc:resent-from:resent-sender:resent-message-id:in-reply-to:references:list-id:list-help:list-unsubscribe:list-subscribe:list-post:list-owner:list-archive”;

sign_condition = “if (header_exists(‘From’) and header_exists(‘To’) and header_exists(‘Subject’)) { return ‘yes’; } return ‘no’;”;

}

Replace “example.com” with your own domain name.

The “selector” specifies the name of the DKIM key to be used. Step 2: Save and exit the file, then restart the Rspamd service to apply the changes:

sudo systemctl restart rspamd

Updating DNS Zone Records with DKIM Public Key

To enable DKIM verification by email recipients, you need to update your DNS zone records with the DKIM public key. Here are the steps to do this:

Step 1: Open the DNS management interface provided by your DNS hosting provider.

Step 2: Add a TXT record with the following format:

default._domainkey IN TXT “v=DKIM1;k=rsa;p=DKIM_PUBLIC_KEY”

Replace “DKIM_PUBLIC_KEY” with the actual DKIM public key, which can be found in the .key.pub file generated by rspamadm in the previous step. Step 3: Save the changes and allow some time for the DNS records to propagate.

Creating DMARC Record

Implementing DMARC Policy

DMARC allows you to specify policies for handling emails that fail authentication. Here’s how to implement a DMARC policy:

Step 1: Open the DNS management interface and navigate to the TXT records for your domain.

Step 2: Add a TXT record with the following format:

_dmarc.yourdomain.com. IN TXT “v=DMARC1; p=quarantine; rua=mailto:[email protected]; ruf=mailto:[email protected]; sp=reject; adkim=s; aspf=s”

Replace “yourdomain.com” with your own domain name.

The “p” tag sets the DMARC policy. In this example, it is set to “quarantine,” which means that emails that fail DMARC authentication will be placed in the recipient’s spam folder.

You can set it to “reject” for a stricter policy. The “rua” and “ruf” tags specify the email addresses to receive aggregate and forensic DMARC reports, respectively.

Updating DNS Zone Records with DMARC Record

To enable DMARC enforcement, you need to update your DNS zone records with the DMARC record. Here are the steps to do this:

Step 1: Open the DNS management interface and navigate to the TXT records for your domain.

Step 2: Add a TXT record with the following format:

_dmarc IN TXT “v=DMARC1; p=quarantine; rua=mailto:[email protected]; ruf=mailto:[email protected]; sp=reject; adkim=s; aspf=s”

Replace “example.com” with your own domain name and “[email protected]” with the email address where you want to receive DMARC reports. Step 3: Save the changes and allow some time for the DNS records to propagate.

Conclusion

By creating DKIM keys and DMARC records, you can enhance the security and authenticity of your email server. DKIM ensures that incoming emails can be verified as coming from a trusted source, while DMARC helps prevent email spoofing and phishing attacks.

By following the steps outlined in this article, you can effectively implement DKIM and DMARC to improve the deliverability and authenticity of your emails. Remember to test your configuration and monitor the DMARC reports regularly to ensure that everything is functioning as intended.

In conclusion, implementing DKIM keys and DMARC records is crucial for enhancing the security and authenticity of your email server. By following the steps outlined in this article, you can create DKIM keys using rspamadm, configure Rspamd to use them, update DNS zone records with the DKIM public key, and implement a DMARC policy.

These measures help prevent spam, phishing attacks, and email spoofing, improving the deliverability and trustworthiness of your emails. Remember to regularly monitor DMARC reports to ensure your email server’s security is maintained.

By prioritizing these email authentication methods, you can establish a more reliable and trustworthy email communication system.

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