Mail server monitoring provides an opportunity to check performance and availability while enabling administrators to identify and handle issues that could delay mail delivery.

Today, electronic mail is still one of the most effective and reliable communication tools for businesses, organizations, and individuals. However, the mail systems comprise several technologies which are prone to fail due to internal and external factors.

To ensure good health and proper operation, it is good practice to continuously observe the mail system.

What are mail servers?

Mail servers are hardware and software technologies for receiving, sending, forwarding, storing, and archiving email messages.

Among the major components is the mail transfer agent (MTA). The MTA is responsible for accepting incoming mails and routing or forwarding them to the target recipient. Typical applications that provide mail transfer agent services include Postfix, qmail, Exim, and Microsoft Exchange Server.

Usually, mail servers exchange emails via different protocols. For example, the incoming mail servers use POP3 or IMAP protocols to save and send mail to the inbox while the outgoing uses SMTP for sending out emails.

Additionally, most email systems support security mechanisms such as authentication and encryption using transport layer security (TLS) to prevent unauthorized access and protect messages in transit.

Usually, mail servers rely on various hardware and software technologies to receive and forward emails. The hardware includes powerful computer servers with reasonable bandwidth to handle the email traffic. Some common mail server software includes Microsoft Exchange Server, Postfix, qmail, Exim, and others.

What is mail server monitoring?

The goal of monitoring mail servers is to ensure that users can send and receive emails efficiently. It also checks the backing up and archiving of emails.

Therefore, you should measure metrics, such as the mail server response times, uptime, network statistics, and more. You should also check for outages and delays in delivering email messages.

Additionally, you need to check the email queues and ensure they are short. Otherwise, if a mail server cannot send emails, they will remain in the email queue, which will continue to grow. Consequently, this will cause delays.

Monitoring Postfix, qmail, Exim, Microsoft Exchange, and other mail transfer agents is critical in ensuring uninterruptible communication. In addition, you should ensure that emails are delivered promptly and archived securely.

Towards this, you should monitor services such as POP3, IMAP, or SMTP. If these services do not function properly, the server may have problems delivering email messages.

What do you monitor on a server?

Mail server monitoring involves checking the health and performance of the underlying technologies and services. This ensures prompt email delivery, backing up of messages, and more.

The monitoring involves observing and checking the health of the mail server resources to ensure that they are sufficient to meet the organization’s needs. Further, it checks the CPU utilization, disk and memory usage, network traffic and activity levels, and other metrics.

Obtaining the various metrics enables administrators to plan well, predict failures, and address issues before failure occurs. It also helps in capacity planning.

Generally, successful mail server monitoring helps to quickly identify and address bottlenecks and issues and hence ensures acceptable operation of the mail servers.

Other metrics that require monitoring on any type of server include disk usage, load and memory, and CPU usage.

How do I monitor my email server?

Most operating systems and mail server software include utilities that show the status of the resources. However, this is costly and inefficient since it requires a dedicated person to check the service manually.

Fortunately, good mail server monitoring tools, such as Checkmk provide automated, efficient, and reliable monitoring. Checkmk has several plug-ins for the popular mail servers and services, and can continuously check the SMTP, POP3, and IMAP services to ensure availability and performance.

Checkmk is easy to set up, allowing you to begin monitoring in only a few minutes. Additionally, Checkmk does not rely on email alerts. If your email communication breaks down, Checkmk can notify you of incidents via Slack, SMS, fax, or another communication method.

Services of a Postfix mail server in Checkmk

Checkmk is suitable for monitoring Windows mail servers. It comes with a powerful Windows agent and a broad set of monitoring extensions for Microsoft Exchange. Further, it integrates with other systems such as Microsoft Azure and Microsoft Hyper-V. For example, if you decide to move your mail servers to the cloud as part of your migration to Microsoft Office 365, you can use Checkmk to ensure uninterrupted operations.

Additionally, you can track the effects of the changes such as when you change the mail servers or move them to the cloud. Comparing the monitoring data provides an opportunity to determine whether your systems are working faster or slower following the migration.

You can also keep an eye on the validity of certificates and find out if the server is routing mail traffic via unencrypted ports. Finally, you can enhance monitoring data security by encrypting the Checkmk data.

How do I monitor email activity?

Ultimately an administrator’s objective is to ensure that emails sent to and from the company’s employees and systems are running smoothly. Apart from monitoring the server components and software, it is important to monitor email activity too.

With Checkmk’s integrated graphing and reporting tools, you can reliably detect anomalies and critical events on your mail servers.

The graph below shows the mail queue in a Postfix mail server. For example, you can immediately detect when the email queue is getting too long. Generally, if it cannot send emails, the messages will remain in the mail queue, which will continue to grow as a result.

Monitoring of a mail queue on a Postfix mail server in Checkmk


Monitoring allows IT teams to determine the health and response times of their mail servers. It provides useful insights and visibility into the mail servers.

While administrators, can perform the monitoring manually, this is a costly and ineffective means of using resources. As such, it is best practice to use automated email server monitoring tools such as Checkmk. 

Today, Checkmk is one of the top and most effective monitoring tools that help organizations to optimize their mail servers and ensure uninterruptible communication.