Free round-trip SMTP monitoring
for businesses that depend on email.
Small email delays can be costly. MailFlowMonitoring continuously tests your email infrastructure by sending test emails and tracking responses. Detect issues before they impact your users.
Trusted by enterprises, SaaS companies, and government
How round-trip monitoring works
Continuous testing ensures your email infrastructure is always operational.
We send test emails
Our monitoring endpoints continuously send test emails to addresses you specify in your domain, simulating real email traffic.
Your server auto-responds
Configure your SMTP server to automatically respond to our test emails. We track response times and delivery success.
Instant alerts on issues
If responses fail or exceed your configured thresholds, we immediately alert you via email, SMS, webhook, or PagerDuty.
What round-trip monitoring validates
- MX records are correctly configured for your SMTP servers
- SMTP servers and relay software are up and running
- Internet connection is active (for self-hosted or co-located servers)
- Spam filters are not delaying or blocking legitimate email delivery
- Complete email routing path is functioning correctly
Monitor your mail flow
Round-trip SMTP and IMAP monitoring with performance metrics and header analysis.
Round-trip Email Tests
Continuous inbound and outbound email tests with complete header analysis and transaction logging.
Multi-channel Alerts
Configurable real-time alerts via email, SMS, webhook, PagerDuty, and Slack when thresholds are exceeded.
Performance Metrics
Track response times, delivery success rates, and historical statistics to optimize mail server performance.
Customizable Timeouts
Configure monitoring intervals and timeout thresholds based on your specific business requirements.
Transaction Logging
Complete log of all test emails sent and received, helping diagnose routing and blacklisting issues.
24/7 Monitoring
Day and night continuous testing ensures you are alerted to disruptions the moment they happen.
Explore the dashboard
Intuitive interface with powerful monitoring features.
You're in complete control
Scalable monitoring
Start with one free monitor and scale up as your infrastructure grows.
Custom intervals
Control how often we check your servers, from every minute to hourly.
Flexible thresholds
Set RTT thresholds and delay rates that match your requirements.
Multi-channel alerts
Email, SMS, webhook, PagerDuty, Slack — your channel, your rules.
Built by email infrastructure experts
As an email service provider, we needed to track mail flow problems through a large number of inbound email servers. Unlike services that deliver to a single MX record, we needed to specify individual IP addresses for message delivery.
We found existing services charging $500+ per month with limited flexibility. So we built our own solution. Since launching in 2018, MailFlowMonitoring has grown to serve over 10,000 businesses worldwide.
We built the tool we wanted to use ourselves, with the alerting integrations modern teams need. Whether you're monitoring a single mail server or complex multi-server infrastructure, we have a plan that fits.
Our Email Infrastructure Suite
Start monitoring your email infrastructure
Join thousands of businesses ensuring their email reliability. Setup takes less than 10 minutes.