PRTG Manual: SMTP&POP3 Round Trip Sensor

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.

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.

You 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.

Only ASCII characters are allowed.

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.

We recommend that you use the default value.

If 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).

If 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.

To use your Google account credentials, enter your Google email address. For example, [email protected].

Password

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

Enter a password for SMTP authentication. Enter a string.

To use your Google account credentials, enter your Google application password. For more information, see the Knowledge Base: How can I use my Google account credentials in PRTG?.

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.

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.

If 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.

If 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.

IP Address/DNS Name

Specify the POP3 server. Enter a valid IP address or Domain Name System (DNS) name.

Port

Specify the port that the sensor uses for the POP3 connection. The default port for unsecure connections is 110 and the default port for secure connections is 995. The actual setting depends on the server you connect to. Enter an integer.

We recommend that you use the default value.

If 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 POP3 server. PRTG continuously checks the mailbox in this scanning interval until the email arrives. Enter an integer.

Maximum Trip Time (Sec.)

Enter the maximmum number of seconds an email can take to arrive in the POP3 mailbox. PRTG continuously checks the mailbox in the interval that you specify above until the email arrives. If it does not arrive within the maximum trip time, the sensor triggers an error message. Enter an integer.

POP3 Authentication Method

Select the authentication method for the POP3 connection:

• Without login (default): Only monitor the connection to the POP3 server.
• User name and password: Log in to the POP3 server with user name and password.
  This is a simple login. It is not secure.
• 128-bit MD5 hash value (APOP): Send the password in an encrypted form using APOP.
  The POP3 server that you connect to must support this option.

User Name

This setting is only visible if you select User name and password or 128-bit MD5 hash value (APOP) above.

Enter a user name for POP3 authentication. Enter a string.

To use your Google account credentials, enter your Google email address. For example, [email protected].

Password

This setting is only visible if you select User name and password or 128-bit MD5 hash value (APOP) above.

Enter a password for POP3 authentication. Enter a string.

To use your Google account credentials, enter your Google application password. For more information, see the Knowledge Base: How can I use my Google account credentials in PRTG?.

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.

If 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.

If 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.

Result Handling

Define what PRTG does with the sensor result:

• Discard result (default): Do not store the sensor result.
• Store result: Store the sensor result and the last response 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.

This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.

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

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.

You can set a different primary channel later by clicking 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.
  You 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.

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 (POP3)

The response time of the POP3 server

Response Time (SMTP)

The response time of the SMTP server

Total

The sum of the response time of the SMTP server and the POP3 server

This channel is the primary channel by default.