Connectivity logging records the connection activity of the outgoing message delivery queues that exist on computers that have the Hub Transport server role or Edge Transport server role installed. The purpose of the connectivity log is not to track the transmission of individual e-mail messages. The connectivity log tracks the connection activity from the sending queue to the destination Mailbox server, smart host, or domain.
Agent logs record the actions that are performed on a message by specific anti-spam agents that are installed and configured on a computer that is running Microsoft Exchange Server 2007 that has the Edge Transport server role or the Hub Transport server role installed
A message tracking log is a detailed log of all message activity as messages are transferred to and from a computer that is running Microsoft Exchange Server 2007 and that has the Hub Transport server role, the Mailbox server role, or the Edge Transport server role installed. Exchange servers that have the Client Access server role or Unified Messaging server role installed don’t have message tracking logs. You use message tracking logs for message forensics, mail flow analysis, reporting, and troubleshooting.
Protocol logging records the Simple Mail Transfer Protocol (SMTP) conversations that occur between e-mail servers as part of message delivery. These SMTP conversations occur on Send connectors and Receive connectors that are configured on Microsoft Exchange Server 2007 servers that have the Hub Transport server role or the Edge Transport server role installed. You can use protocol logging to diagnose mail flow problems.
A single SMTP conversation that represents the sending or receiving of a single e-mail message generates multiple SMTP events. These SMTP events cause multiple lines to be written to the protocol log. Multiple SMTP conversations that represent the sending or receiving of multiple e-mail messages can occur at the same time. This creates protocol log entries from different SMTP conversations that are interspersed. However, it is easy to use the session-id and sequence-number fields to sort the protocol log entries by SMTP conversation.