Windows Service Name: SMTPSVC
Service Description: Simple Mail Transport Protocol (SMTP).

WMI Class: Win32_PerfRawData_SMTPSVC_SMTPServer
Property: MessagesDeliveredTotal
Description: Total number of messages delivered to local mailboxes.

WMI Class: Win32_PerfRawData_SMTPSVC_SMTPServer
Property: MessagesSentTotal
Description: Total number of outbound messages sent.

WMI Class: Win32_PerfRawData_SMTPSVC_SMTPServer
Property: RemoteQueueLength
Description: Number of messages in the remote queue.

WMI Class: Win32_PerfRawData_SMTPSVC_SMTPServer
Property: LocalQueueLength
Description: Number of messages in the local queue.