How to Create Devices and Targets

How It Works

SMTP-POP3/IMAP monitoring performs end-to-end availability monitoring of your mail servers. First, a monitoring agent tests the SMTP server by sending a test email to the specified email address. After the test email is sent, the agent attempts to log in and retrieve the email from a POP3/IMAP server. If the SMTP or POP3/IMAP steps experience an error, or the email is not found within a specified time-out period, an error is recorded.

SMTP servers often accept connections from a specific list of hosts only. To ensure seamless monitoring, whitelist Dotcom-Monitor monitoring agents within your firewall settings. You can find a full list of Dotcom-Monitor network location IP addresses here.

Creating a Target

Once you have created a device and are adding or editing an SMTP-POP3 task, you will be prompted to configure a network connection to Outgoing and Incoming Mail Servers.

Configuration Tips

It is recommended to disable the Allow Simultaneous Checks option due to the possible conflict in email processing while checking the inbox by several agents simultaneously.

Outgoing Server Settings

Send Email to

Enter the destination email address. Test emails will be sent to the provided address.

Use a dedicated email address for each task, as sharing the address may cause mailbox access conflicts.

To avoid monitoring errors, do not make any changes to the provided email inbox. All test emails will be deleted automatically after the mail receiving operation.

Send Using MX Record

MX (Mail Exchange) Record points to IP addresses for your domain mail server.  In other words, MX Records specify what mail server should be used to handle your domain’s email.

When enabled (the Yes option), Dotcom-Monitor looks up for a target mail server assigned to the domain (the Send Email to field) using MX Records.

In the case of using MX Records, the non-secure connection is used.

MX records are used according to the preference numbers provided in each record. The MX record with the lower preference number has the highest priority and will be tried first to connect to the mail server. If the mail server with the highest priority is not responding, the next MX record, according to its priority, will be used. If all domain mail servers are not available, an error for the device will be generated.

If No is selected, a mail server provided in the Target SMTP Server field is used to send the email.

Target SMTP Server

Enter the SMTP server address and port number (optionally) you want to retrieve test email from. You can provide a hostname or an IP address.

Default ports:

  • SMTP: 25
  • SMTPS (over SSL): 465

Secure Connection

When enabled, SMTP over SSL/TLS will be requested.


Your SMTP server might not require an authorization. Otherwise, fill in the server access credentials.

Web Authentication (Modern Authentication)

If you have Modern Authentication enabled in Exchange Online (authentication against AD via token), provide a username of the account you want to monitor and a random password. The system will omit the password field value upon the authentication process, as modern authentication typically involves the use of tokens.

To continue with the round-trip monitoring setup using modern authentication, please see Using Modern Authentication for Exchange Online | Office 365 | Microsoft 365 Monitoring.

Basic Authentication (Legacy authentication)

Basic Authentication is considered legacy and deprecated. It involves sending the username and password over the network, making it less secure compared to modern authentication methods. Microsoft encourages transitioning to Modern Authentication for improved security.

If your Exchange Online supports username-password based authentication to connect to Exchange Online mailboxes in Office 365 or Microsoft 365, please enter a username and password of the account you want to monitor.

Operation Timeout

Specify the email sending timeout, in seconds. The sending time includes SMTP connection time and sending operation time.

If you have duplicated emails left in the inbox, and a task failure occurs, the possible reason is False Positive Check after operation timeout error.

From Email

Specify an address to set in the From field of the test email.

If the System Default option is selected, a unique address of a monitoring agent (e.g. which initiates the task execution will be set in the From field.

If the target SMTP Server requires secure connection and authentication (the Username/Password fields are specified), and the System Default option is selected, the From field will contain the same address as provided in the Send Email to field.

If validation errors occur, make sure the system default address doesn’t go to spam instead of the inbox.

The Custom option allows you to specify an email address to set in the From field (regardless of SMTP authentication).

Incoming Server Settings

Target Mail Server

Select the protocol type you wish to test: POP3 or IMAP (ver. 4.1)

Enter the POP3 or IMAP server address and port number. This could be the URL or the IP address.

Make sure your server supports the appropriate protocol type before you continue.

Secure Connection

When enabled – connection over SSL/TLS will be requested.


Enter a username and password for POP3/IMAP authentication.

Operation Timeout

Specify the timeout for mail receiving operation, in seconds. During the receiving operation, Dotcom-Monitor will scan all messages in the incoming mailbox until the test email is found, or until the Operation Timeout is reached.  To reduce the time it takes to receive the test email, it is recommended to keep the incoming box empty.

Advanced settings

Email Timeout

Specify the email delivery timeout time in minutes. The receiving operation will be repeated until the Email Timeout is reached. You will receive an alert if the email is not found in the incoming box after the specified time.

By default, email timeout is set to 10 minutes, but you can specify a custom timeout. Note that the maximum timeout time supported by Dotcom-Monitor is one hour.

Since Dotcom-Monitor waits for the delivery of a test email for the time specified by the Email Timeout value, no further device tasks will be launched until the test concludes, regardless of the specified monitoring frequency. This can significantly affect the frequency of monitoring, therefore, it is highly recommended to make sure the monitoring frequency value is larger than the Email Timeout value.

To set up a task with a large Email Timeout value, create a separate device with a single task.

Prepare and Post Script

The fields can contain C# code, which can be used for specific POST, GET, URL data or for validating or publishing custom headers. Please see the Using Prepare Script and Post Script article or contact technical support for more details on usage.

DNS Options

The DNS Options feature allows users to choose how domain name server (DNS) requests are conducted during a monitoring task.

To specify the mode of resolving hostnames, in the DNS Resolve Mode section, select one of the available modes. For more details on the feature configuration, see DNS Mode Options.

The Custom DNS Hosts section allows to set up the mapping of IP addresses to hostnames. IPv6 and IPv4 DNS resolution is supported.

To specify the mapping, enter the IP address and the hostname in the corresponding fields.


See also: DNS Mode Options.