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 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.

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

SMTP&IMAP Round Trip Sensor

SMTP&IMAP Round Trip Sensor

i_square_cyanFor a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

Sensor in Other Languages

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

Remarks

Consider the following remarks and requirements for this sensor:

Remark

Description

Performance impact

This sensor has a high performance impact. We recommend that you use no more than 200 of this sensor on each probe.

Parent device

This sensor requires that the parent device is an SMTP server.

SRP ciphers

This sensor does not support Secure Remote Password (SRP) ciphers.

Microsoft 365 mailboxes

This sensor does not support Microsoft 365 mailboxes. If you want to monitor a Microsoft 365 mailbox, use the Microsoft 365 Mailbox sensor.

IPv4

This sensor only supports IPv4.

Dedicated email accounts

Use dedicated email accounts with this sensor. Make sure that each sensor uses its own email accounts.

Basic Sensor Settings

Basic Sensor Settings

Basic Sensor Settings

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

  • imapsensor
  • mailsensor
  • roundtrip

i_square_cyanFor more information about basic sensor settings, see section Sensor Settings.

Email Settings

Email Settings

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.

i_round_blueFor 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.

i_round_redOnly ASCII characters are allowed.

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

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

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

Step 1: Send Email Using Parent Device (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 that you connect to. Enter an integer.

i_round_blueWe recommend that you use the default value.

i_round_blueIf the connection is unsuccessful, try a different port number.

Timeout for SMTP Connection (Sec.)

Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).

i_round_blueIf the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.

SMTP Authentication Method

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

  • None (default): Do not use any authentication method.
  • User name and password: Authenticate against the SMTP server via user name and password.

User Name

This setting is only visible if you select User name and password above.

Enter a user name for SMTP authentication. Enter a string.

Password

This setting is only visible if you select User name and password above.

Enter a password for SMTP authentication. Enter a string.

Additional Text for Email Subject

PRTG automatically creates the subject part of the round trip email. The subject 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

Connection Security

Connection Security

Setting

Description

Transport-Level Security

Define how the sensor handles the security of the connection:

  • Use transport-level security if available using StartTLS: Try 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: Try 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: Try to connect to the server via an SSL/TLS-secured connection and StartTLS. If the server does not support this, the sensor shows the Down status.
  • Enforce transport-level security (default): Try to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor shows the 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 emails that the sensor sends.

Step 2: Check an IMAP Mailbox until Email Arrives

Step 2: Check an IMAP Mailbox until Email Arrives

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, for example INBOX.

i_round_redThe IMAP mailbox or folder name must not match the sender of the email in the From field. Otherwise, the sensor might incorrectly interpret unsuccessful round trips 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.

i_round_blueWe recommend that you use the default value.

i_round_blueIf the connection is unsuccessful, 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.

Maximum Trip Time (Sec.)

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

User Name

Enter a user name for IMAP authentication. Enter a string.

Password

Enter a password for IMAP authentication. Enter a string.

i_round_redThe password must not contain spaces, percent signs (%), or the character combination !*.

Search Method

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

  • Search for the 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 emails 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

Connection Security

Connection Security

Setting

Description

Transport-Level Security

Define how the sensor handles the security of the connection:

  • Use transport-level security if available using StartTLS: Try 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: Try 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: Try to connect to the server via an SSL/TLS-secured connection and StartTLS. If the server does not support this, the sensor shows the Down status.
  • Enforce transport-level security (default): Try to connect to the server via an SSL/TLS-secured connection. If the server does not support this, the sensor shows the 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

Debug Options

Debug Options

Setting

Description

Result Handling

Define what PRTG does with the sensor result:

  • Discard result (default): Do not store the sensor result.
  • Store result: Store the last sensor result in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This setting 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 Monitor instance.

i_round_blueIn a cluster, PRTG stores the result in the PRTG data directory of the master node.

Sensor Display

Sensor Display

Sensor Display

Setting

Description

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel 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 this sensor shows different channels:

  • 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 select Stack channels on top of each other above.

Select a unit from the list. PRTG stacks all channels with this unit 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 these settings are inherited from objects that are higher in the hierarchy. We recommend that you 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 and to display its options.

i_square_cyanFor more information, see section Inheritance of Settings.

Channel List

i_round_blueWhich channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.

Channel

Description

Downtime

In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status

Response Time (IMAP)

The response time of the IMAP server

Response Time (SMTP)

The response time of the SMTP server

Total

The sum of the response time of the IMAP server and the SMTP server

i_round_blueThis channel is the primary channel by default.

More

i_square_blueKNOWLEDGE BASE

What security features does PRTG include?