How to Set Up Mail Forwarding in Procmail on Ubuntu? [Step-by-Step Guide]

Introduction

Email forwarding is an essential task for system administrators and email power users. With Procmail, you can automate email filtering and forwarding efficiently on Ubuntu. This guide will walk you through everything you need to know to set up and optimize Procmail for mail forwarding.

What is Procmail?

Procmail is a mail processing utility for Unix-based systems, including Ubuntu. It filters, sorts, and forwards emails based on user-defined rules called recipes. Procmail is widely used for:

• Automatic email sorting
• Spam filtering
• Email forwarding to multiple addresses
• Running scripts based on incoming emails

Why Use Procmail for Mail Forwarding?

Using Procmail for mail forwarding offers several benefits:

• Flexibility: You can define multiple conditions and actions.
• Automation: Once set up, Procmail handles emails without manual intervention.
• Customization: Supports regex-based filtering and scripting.
• Integration: Works seamlessly with other mail servers like Postfix and Sendmail.

Prerequisites

Before setting up Procmail, ensure you have the following:

• An Ubuntu server or desktop (version 18.04, 20.04, or later)
• A configured mail server (Postfix, Sendmail, or Exim)
• Basic knowledge of the command line
• Administrative or sudo privileges

Installing Procmail on Ubuntu

Procmail is available in Ubuntu’s default repositories. Install it using:

sudo apt update
sudo apt install procmail

Verify installation:

procmail -v

Configure Procmail for Mail Forwarding

Step 1: Create .procmailrc File

Each user who wants to set up mail forwarding must create a .procmailrc configuration file in their home directory. Navigate to the user’s home directory and create the file:

cd ~
nano .procmailrc

Step 2: Set Up Basic Procmail Configuration

Add the following lines to the .procmailrc file:

SHELL=/bin/bash
MAILDIR=$HOME/Maildir/
LOGFILE=$HOME/.procmail.log
DEFAULT=$MAILDIR
VERBOSE=yes

Step 3: Configure Mail Forwarding Rules

To forward emails to another address, use the following rule:

:0
* ^TO_myemail@example.com
! forwardemail@example.com

Explanation:

• :0 starts the rule definition.
• ^TO_myemail@example.com matches incoming emails sent to myemail@example.com.
• ! forwardemail@example.com forwards the matched email to forwardemail@example.com.

Step 4: Enable Global Procmail Forwarding (Optional)

For system-wide mail forwarding, configure Procmail as the default MTA mail delivery agent by editing the Postfix configuration file:

sudo nano /etc/postfix/main.cf

Add or modify the following line:

mailbox_command = /usr/bin/procmail

Restart Postfix to apply changes:

sudo systemctl restart postfix

Testing Mail Forwarding

Send a test email to verify that mail forwarding works as expected:

echo "Test email" | mail -s "Test Subject" myemail@example.com

Check the recipient’s inbox to confirm the forwarded email.

Advanced Mail Forwarding Rules

Forward emails only if they contain specific keywords:

:0
* ^Subject:.*Important
! important@example.com

Automating Procmail with Cron Jobs

Run a script daily to clean old emails:

crontab -e

Add following code to configure corn job as per your convinince to run the job.

0 2 * * * find ~/Mail -type f -mtime +30 -delete

Alternative Methods for Mail Forwarding

• Postfix Aliases: Modify /etc/aliases
• Gmail Forwarding: Use built-in filters

1- Can I forward emails to multiple addresses?

Yes, separate addresses with a comma:

! email1@example.com, email2@example.com

2- How do I log Procmail actions?

Enable logging in .procmailrc:

LOGFILE=$HOME/.procmail.log
VERBOSE=yes

3- Can Procmail filter spam?

Yes, use recipes to detect spam keywords.

4- How do I disable Procmail temporarily?

Rename .procmailrc

mv ~/.procmailrc ~/.procmailrc.bak

5- What happens if Procmail fails?

Emails are delivered to the default mailbox.

6- Does Procmail work with cloud-based email providers?

Only if they support forwarding via SMTP/IMAP.

Setting up mail forwarding in Procmail on Ubuntu is a straightforward process that enhances email management capabilities. By configuring Procmail with custom rules, users can efficiently filter and forward emails to desired destinations.

How to Set Up Mail Forwarding in Postfix on Linux – A Complete Guide

Set Up Mail Forwarding in Sendmail on Linux?