Custom alerts and data visualization let you quickly identify and prevent slow response times, downtime, and other email connectivity issues.
Remember when the likes of Slack and other cloud-based instant messaging, productivity, and collaboration apps promised to replace email?
Yes. About that.
In 2023, we collectively sent 347.3 billion emails. Every. Single. Day.
And we don’t use email just to communicate and collaborate. It’s a sales tool, a marketing tool, a customer engagement tool, a complaint-handling tool… you get the idea.
With so much riding on email, you can't afford SMTP server delays or disruption. And, with Paessler PRTG’s powerful preconfigured SMTP monitoring sensors, you won't have to.
Pick your preferred parameters, and PRTG will keep an eagle eye on all your critical mail server metrics and alert you if there’s a risk they might go down. Which means more uptime, better email delivery, and happier colleagues, without overwhelming your to-do list.
Getting started with PRTG as your SMTP monitoring tool couldn't be simpler. The automatic network discovery detects every available network component within your chosen IP address range, and assigns the appropriate sensors. Tweak the monitoring parameters to suit, and let it do its work. Job done.
A single, unified view of your email services' health… and that of your entire network. Whether you have a basic setup or a complex distribution with multiple operating systems or virtualized infrastructure, PRTG enables you to keep an eye on everything without switching between monitoring environments.
Because you can see all your mission-critical parameters at a glance, in real time, it’s easier to pinpoint the root cause of a problem. PRTG even sends you automatic notifications via SMS, email (there you have it), or other methods when a metric goes above or below your preferred performance thresholds.
Diagnose network issues by continuously tracking the availability and performance of your SMTP servers and other mail servers such as Microsoft Exchange. Show incoming and outgoing emails, response times, server authentication, and other key metrics in real time. Visualize monitoring data in clear graphs and dashboards to identify problems more easily. Gain the overview you need to troubleshoot all kinds of email connectivity and routing issues.
Device tree view of the complete monitoring setup
Custom PRTG dashboard for keeping an eye on the entire IT infrastructure
Live traffic data graph in PRTG
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PRTG’s SMTP sensors track all your critical email health stats round the clock, ensuring SMTP servers are working efficiently… and that important emails don't get delayed or remain undelivered.
Our all-in-one network monitoring tool has three preconfigured SMTP sensors that keep an eye on response time and email round trip time.
Use a Windows SMTP service? Our Windows SMTP service sent and service received sensors can keep an eye on how many emails you’ve sent and received via WMI or Windows performance counters.
You can also monitor your Microsoft Exchange mailbox and mail queue.
PRTG comes with more than 250 native sensor types for monitoring your entire on-premises, cloud, and hybrid cloud environment out of the box. Check out some examples below!
The SMTP sensor monitors a mail server using the Simple Mail Transfer Protocol (SMTP). It can show the following:
The SMTP&IMAP Round Trip sensor monitors the time it takes for an email to reach an Internet Message Access Protocol (IMAP) mailbox using the Simple Mail Transfer Protocol (SMTP). It sends an email via the parent device (an SMTP server) and then scans a dedicated IMAP mailbox until the email arrives. It can show the following:
The SMTP&POP3 Round Trip sensor monitors the time it takes for an email to reach a Post Office Protocol version 3 (POP3) mailbox using the Simple Mail Transfer Protocol (SMTP). It sends an email using the parent device (an SMTP server) and then scans a dedicated POP3 mailbox until the email comes in. It can show the following:
The Exchange Mailbox (PowerShell) sensor monitors mailboxes of an Exchange server. It can show the following:
See the PRTG Manual for a list of all available sensor types.
Custom alerts and data visualization let you quickly identify and prevent slow response times, downtime, and other email connectivity issues.
PRTG is set up in a matter of minutes and can be used on a wide variety of mobile devices.
“Excellent tool for detailed monitoring. Alarms and notifications work greatly. Equipment addition is straight forward and server initial setup is very easy. ...feel safe to purchase it if you intend to monitor a large networking landscape.”
Partnering with innovative IT vendors, Paessler unleashes synergies to create
new and additional benefits for joined customers.
Integrating monitoring results from PRTG into NetBrain maps makes the foundation for network automation.
Combining PRTG’s broad monitoring feature set with IP Fabric’s automated network assurance creates a new level of network visibility and reliability.
Combining their tools to a powerful solution for advanced analysis and automation, KnowledgeRiver and Paessler enable IT teams to ensure best performance for their infrastructure and networks.
Real-time notifications mean faster troubleshooting so that you can act before more serious issues occur.
Network Monitoring Software – Version 25.3.110.1313 (August 27, 2025)
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SMTP (Simple Mail Transfer Protocol) is email's postal service that transfers messages between servers. SMTP monitoring is crucial because email remains a business-critical communication channel. Effective SMTP monitoring helps prevent delivery failures, detects performance issues before they impact users, and ensures compliance with service level agreements.
Without proper SMTP monitoring, organizations risk communication disruptions that can affect productivity, customer relationships, and revenue.
PRTG establishes connections with mail servers to track key performance metrics in real-time. SMTP monitoring sensors verify server availability, measure response times, and test complete email delivery cycles. By implementing comprehensive SMTP monitoring, administrators receive immediate alerts when issues arise.
SMTP monitoring capabilities include tracking both sending and receiving processes, with options to configure authentication credentials and test parameters according to your specific requirements.
While 200 milliseconds or under is generally considered ideal for SMTP server response, actual performance varies based on network configuration and provider capabilities. Effective SMTP monitoring establishes your environment's baseline performance metrics, allowing you to set appropriate thresholds for alerts.
Regular SMTP monitoring helps identify trends and potential bottlenecks before they impact email delivery. Without consistent SMTP monitoring, gradual performance degradation may go unnoticed until users report problems.
PRTG uses preconfigured sensors to monitor the sending and receiving of emails that originate in your system. It starts by sending an email to a given email address. This allows you to immediately see whether – and how fast – the email reaches the recipient, and how long it takes for the recipient to retrieve the email via POP3. If the delivery and retrieval are successful, the email is automatically deleted.
The SMTP monitoring functionality sends test emails to specified addresses and measures complete delivery cycles. This end-to-end SMTP monitoring approach verifies both sending capabilities and retrieval times via POP3 or IMAP.
For advanced analysis, SMTP monitoring leverages regular expression matching within log files to identify specific patterns, delivery failures, or security issues. After successful verification, the test emails are automatically deleted, making SMTP monitoring completely transparent to end users.
PRTG’s biggest benefit is that it’s an all-in-one monitoring solution (as your higher-ups would put it). In other words, it enables you to keep an eye not just on SMTP servers, but on every single component that forms part of your network, without having to switch between different monitoring environments. With support for all major protocols – including SNMP, WMI, Windows performance counters, flow, SSH, HTTP and HTTPS, FTP, and more – PRTG can monitor every component and parameter imaginable, no matter how complex your network is.
In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, for example the traffic of a switch port, the CPU load of a server, or the free space on a disk drive. On average, you need about 5-10 sensors per device or one sensor per switch port.
Paessler conducted trials in over 600 IT departments worldwide to tune its network monitoring software closer to the needs of sysadmins. The result of the survey: over 95% of the participants would recommend PRTG – or already have.
Paessler PRTG is used by companies of all sizes. Sysadmins love PRTG because it makes their job a whole lot easier.
Bandwidth, servers, virtual environments, websites, VoIP services – PRTG keeps an eye on your entire network.
Everyone has different monitoring needs. That’s why we let you try PRTG for free.
