PRTG Manual: SMTP&IMAP Round Trip Sensor

The SMTP&IMAP Round Trip sensor monitors the time it takes for an email to reach an Internet Message Access Protocol (IMAP) mailbox after being sent using the Simple Mail Transfer Protocol (SMTP). It sends an email using the parent device (an SMTP server) and then scans a dedicated IMAP mailbox until this email comes in.

The SMTP&IMAP Round Trip sensor automatically deletes these emails from the mailbox as soon as PRTG has retrieved them. Emails only remain in the mailbox if a timeout or a restart of the PRTG core server occurred during sensor runtime.

The sensor can show the following:

  • Response time of the SMTP server
  • Response time of the IMAP server
  • Sum of both response times
SMTP&IMAP Round Trip Sensor

SMTP&IMAP Round Trip Sensor

Sensor in Other Languages

  • Dutch: SMTP & IMAP Round Trip
  • French: Durée de boucle SMTP&IMAP
  • German: SMTP&IMAP-Übermittlung
  • Japanese: SMTP & IMAP ラウンドトリップ
  • Portuguese: Percurso de ida e volta SMTP&IMAP
  • Russian: Цикл SMTP&IMAP
  • Simplified Chinese: SMTP 和 IMAP 往返
  • Spanish: Ida y vuelta SMTP&IMAP

Remarks

  • The parent device must be an SMTP server.
  • This sensor does not support Secure Remote Password (SRP) ciphers.
  • Use dedicated email accounts with this sensor. If you use more sensors of this type, make sure that each sensor uses its own email accounts.
  • This sensor has a high performance impact.

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Basic Sensor Settings

Click the Settings tab of a sensor to change its settings.

i_round_blueUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Setting

Description

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows tags that the sensor inherits from its parent device, parent group, and parent probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.

i_round_blueIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

  • imapsensor
  • roundtrip
  • mailsensor

Priority

Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority (i_priority_1) to the highest priority (i_priority_5).

Email Settings

Setting

Description

From

Specify the email address of the email's sender. Enter a valid email address.

To

Specify the address that PRTG sends the emails to. Enter a valid email address.

i_round_blueYou can only enter one email address.

HELO Ident

Enter a server name for the HELO part of the mail protocol. For some mail servers, the HELO identifier must be the valid principal host domain name for the client host. For more information, see SMTP RFC 2821.

Step 1: Send Email Using Parent Device (SMTP Server)

i_round_blueIn this step, you configure how PRTG sends the emails. The sensor uses the IP Address/DNS Name of its parent device (an SMTP server).

Setting

Description

Port

Enter the number of the port that the sensor uses to send an email via SMTP. The default port for unsecure connections is 25 and the default ports for secure connections are 465 or 587. The actual setting depends on the server you are connecting to. Enter an integer value. We recommend that you use the default value.

If you do not get a connection, try a different port number.

Timeout for SMTP Connection (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message. Enter an integer value. The maximum value is 900 seconds (15 minutes).

SMTP Authentication Type

Define if you want to use authentication for the SMTP connection:

  • None: Do not use any authentication method.
  • Username/Password: Authenticate against the SMTP server via username and password.

Username

This setting is only visible if you enable Username/password above. Enter a username for SMTP authentication. Enter a string.

Password

This setting is only visible if you enable Username/password above. Enter a password for SMTP authentication. Enter a string.

Additional Text for Email Subject

The subject part of the round trip email is automatically created by PRTG. It consists of the string PRTG Roundtrip Mail:, followed by a unique globally unique identifier (GUID) to correctly identify the email in the IMAP mailbox, for example, PRTG Roundtrip Mail: {5E858D9C-AC70-466A-9B2A-55630165D276}.

Use this field to place your custom text before the automatically created text.

Connection Security

Setting

Description

SMTP Specific

Define the security of the connection:

  • Use transport-level security if available using StartTLS (default): The sensor tries to connect to the server via a Secure Sockets Layer (SSL)/Transport Layer Security (TLS) secured connection and StartTLS. If the server does not support this, the sensor tries to connect without connection security.
  • Use transport-level security if available: The sensor tries to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor tries to connect without connection security.
  • Enforce transport-level security using StartTLS: The sensor tries to connect to the server via an SSL/TLS-secured connection and StartTLS. If the server does not support this, the sensor shows a Down status.
  • Enforce transport-level security: The sensor tries to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor shows a Down status.

i_round_blueIf the sensor connects to a server via StartTLS, the connection is first established without connection security. After the connection has been established, the sensor sends a certain command (StartTLS) over the unsecured connection to negotiate a secure connection via SSL/TLS.

i_round_blueIf the sensor does not use StartTLS, the negotiation of a secure connection happens immediately (implicitly) so that no commands are sent in unencrypted plain text. If no secure connection is possible, no communication takes place.

Step 2: Check an IMAP Mailbox until Email Arrives

i_round_blueIn this step, you configure how to receive the sent emails.

Setting

Description

IP Address/DNS Name

Specify the IMAP server. Enter a valid IP address or Domain Name System (DNS) name.

Mailbox

Specify the IMAP mailbox that you want to check. Enter the IMAP mailbox or folder name.

i_round_redThe IMAP mailbox or folder name must not match the sender of the email you entered in the From field. Otherwise, unsuccessful round trips might be incorrectly interpreted as successful.

Port

Specify the port that the sensor uses for the IMAP connection. The default port for unsecure connections is 143 and the default port for secure connections is 993. The actual setting depends on the server you connect to. Enter an integer value. We recommend that you use the default value.

If you do not get a connection, try a different port number.

Connection Interval (Sec.)

Enter the number of seconds the sensor waits between two connections to the IMAP server. PRTG repeatedly checks the mailbox in this scanning interval until the email arrives. Enter an integer value.

Maximum Trip Time (Sec.)

Enter the number of seconds an email may take to arrive in the IMAP mailbox. PRTG continuously checks the mailbox in the scanning interval that you specify above until the email arrives. If it does not arrive within the maximum trip time, the sensor shows an error message. Enter an integer value.

Username

Enter a username for IMAP authentication. Enter a string.

Password

Enter a password for IMAP authentication. Enter a string.

i_round_redThe password must not contain spaces or percent signs (%).

Search Method

Define how to search for the round trip email in the mailbox:

  • Search email directly (default): Send a SEARCH command to directly find the round trip email on the IMAP server.
  • Search through all available emails: Search through all available messages in the mailbox locally to find the round trip email. This might take some time if you have many emails in your mailbox.

Connection Security

Setting

Description

IMAP Specific

Define the security of the connection:

  • Use transport-level security if available using StartTLS (default): The sensor tries to connect to the server via a Secure Sockets Layer (SSL)/Transport Layer Security (TLS) secured connection and StartTLS. If the server does not support this, the sensor tries to connect without connection security.
  • Use transport-level security if available: The sensor tries to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor tries to connect without connection security.
  • Enforce transport-level security using StartTLS: The sensor tries to connect to the server via an SSL/TLS-secured connection and StartTLS. If the server does not support this, the sensor shows a Down status.
  • Enforce transport-level security: The sensor tries to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor shows a Down status.

i_round_blueIf the sensor connects to a server via StartTLS, the connection is first established without connection security. After the connection has been established, the sensor sends a certain command (StartTLS) over the unsecured connection to negotiate a secure connection via SSL/TLS.

i_round_blueIf the sensor does not use StartTLS, the negotiation of a secure connection happens immediately (implicitly) so that no commands are sent in unencrypted plain text. If no secure connection is possible, no communication takes place.

Debug Options

Setting

Description

Sensor Result

Define what PRTG does with the sensor results:

  • Discard sensor result: Do not store the sensor result.
  • Write sensor result to disk (file names: Result of Sensor [ID].*): Store the last result received from the sensor to the \Logs\sensors subfolder of the PRTG data directory on the probe system (master node, if in a cluster). File names: Result of Sensor [ID].* and Result of Sensor [ID].Data.*. This is for debugging purposes. PRTG overwrites these files with each scanning interval.

i_podThis option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.

Sensor Display

Setting

Description

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

i_round_blueYou can set a different primary channel later by clicking b_channel_primary below a channel gauge on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

  • Show channels independently (default): Show a graph for each channel.
  • Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
    i_round_redYou cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should change them centrally in the root group settings if necessary. To change a setting for this object only, click b_inherited_enabled under the corresponding setting name to disable the inheritance. You then see the options described below.

i_square_cyanFor more information, see section Inheritance of Settings.

Scanning Interval

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

Scanning Interval

Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:

  • 30 seconds
  • 60 seconds
  • 5 minutes
  • 10 minutes
  • 15 minutes
  • 30 minutes
  • 1 hour
  • 4 hours
  • 6 hours
  • 12 hours
  • 1 day

i_round_blueYou can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:

  • Set sensor to down immediately: Set the sensor to the Down status immediately after the first request fails.
  • Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status.
  • Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails.
  • Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails.
  • Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails.
  • Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails.

i_round_blueSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show the Down status. It is not possible to immediately set a WMI sensor to the Down status, so the first option does not apply to these sensors. All other options can apply.

i_round_blueIf you define error limits for a sensor's channels, the sensor immediately shows the Down status. None of the interval options apply.

i_round_blueIf a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Schedules, Dependencies, and Maintenance Window

i_round_blueYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.

Setting

Description

Schedule

Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:

  • None
  • Saturdays
  • Sundays
  • Weekdays
  • Weekdays Eight-To-Eight (08:00 - 20:00)
  • Weekdays Nights (17:00 - 09:00)
  • Weekdays Nights (20:00 - 08:00)
  • Weekdays Nine-To-Five (09:00 - 17:00)
  • Weekends

i_square_cyanYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Schedules.

Maintenance Window

Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:

  • Not set (monitor continuously): Do not set up a one-time maintenance window. Monitoring is always active.
  • Set up a one-time maintenance window: Set up a one-time maintenance window and pause monitoring. You can define a time span for a the pause below.

i_round_blueTo terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the one-time maintenance window.

Maintenance Ends

This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window.

Dependency Type

Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:

  • Use parent: Use the dependency type of the parent object.
  • Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in the Down status or in the Paused status because of another dependency.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in the Down status, the device is paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor is paused if the parent group is paused by another dependency.

i_round_blueTo test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This setting is only visible if you enable Select a sensor above. Click b_search_light and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay.

After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.

i_round_redThis setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

Access Rights

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

User Group Access

Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:

  • Inherited: Inherit the access rights settings of the parent object.
  • No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
  • Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
  • Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
  • Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

i_square_cyanFor more details on access rights, see section Access Rights Management.

Sensor Settings Overview

For more information about sensor settings, see the following sections: