How to Set Up Mail Queue Monitoring

Prerequisites

Before monitoring mail queue, make sure you have:

• Postfix installed
• Root or sudo privileges

Step 1: Check Mail Queue Size

Connect to your VPS:

ssh hxroot@YOUR_SERVER_IP -p 22

mailq | tail -n1

Or:

postqueue -p | wc -l

Step 2: Create Monitoring Script

sudo nano /usr/local/bin/check-mailq.sh

#!/bin/bash
THRESHOLD=50
MAILQ_COUNT=$(postqueue -p | grep -c "^[A-F0-9]")
if [ $MAILQ_COUNT -gt $THRESHOLD ]; then
    echo "Mail queue has $MAILQ_COUNT messages (threshold $THRESHOLD)" | mail -s "Mail Queue Alert" admin@example.com
fi

sudo chmod +x /usr/local/bin/check-mailq.sh

Step 3: Schedule Cron Job

sudo crontab -e

*/15 * * * * /usr/local/bin/check-mailq.sh

Step 4: Monitor with Nagios/Other (Advanced)

Nagios users can use check_mailq plugin.

Step 5: View Detailed Queue Information

postqueue -p

To see why messages are stuck:

sudo tail -f /var/log/mail.log