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Understanding Agent Logging

Exchange 2010
 

Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2

Topic Last Modified: 2009-11-17

Agent logs record the actions performed on a message by specific anti-spam agents installed and configured on a computer running Microsoft Exchange Server 2010 that has the Edge Transport server role or the Hub Transport server role installed. Only the following agents can write information to the agent log:

  • Connection Filter agent

  • Content Filter agent

  • Edge Rules agent

  • Recipient Filter agent

  • Sender Filter agent

  • Sender ID agent

The information written to the agent log depends on the agent, the SMTP event, and the action performed on the message.

The only configurable option for agent logging is the AgentLogEnabled parameter in the EdgeTransport.exe.config application configuration file. By default, agent logging is enabled on Hub Transport servers or Edge Transport servers. The other agent log values that aren't configurable are described in the following list:

  • Path where the agent logs are stored is C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\AgentLog.

  • Maximum size for the individual agent log files is 10 megabytes (MB).

  • Maximum size for the directory that contains the agent log files is 250 MB.

  • Maximum age for the agent log files is 30 days.

The Exchange 2010 server uses circular logging to limit the agent logs based on file size and file age to help control the hard disk space used by the log files.

noteNote:
If you want to keep the agent log files longer than allowed by file age or directory size values that you can't configure, you can create a scheduled task that periodically moves the unused agent log files to a different location.
noteNote:
By default, the transport logging process has a logging level value of 0 (Lowest). If you want Exchange to write an event log entry when circular logging removes a log file, you must change the logging level value of the transport logging process to 5 (Maximum) or 7 (Expert).

Contents

Overview of Transport Agents

Structure of the Agent Log Files

Information Written to the Agent Log

Searching the Agent Logs

Enable or Disable Agent Logging

Looking for management tasks related to agent logging? See Managing Transport Servers.

Agents can only act upon messages at specific points in the SMTP command sequence used to transport the messages through a Hub Transport server or Edge Transport server. These access points in the SMTP command sequence are called SMTP events. Each agent has a priority value that can be assigned. However, the SMTP events must always occur in a specific order. Therefore, the agent priority depends on the SMTP event. If two agents can act on a message during the same SMTP event, the agent that has the highest priority will act on the message first.

The following table lists the SMTP events in order of occurrence and the agents that write information to the agent log in order of priority from highest to lowest for each SMTP event.

SMTP events in order of occurrence and the agents that write information to the agent log in order of priority for each SMTP event

SMTP event Agent

OnConnect

Connection Filter agent

OnMailCommand

Connection Filter agent

Sender Filter agent

OnRcptCommand

Connection Filter agent

Recipient Filter agent

OnEndOfHeaders

Connection Filter agent

Sender ID agent

Sender Filter agent

OnEndOfData

Edge Rules agent

Content Filter agent

For more information about agents, SMTP events, and agent priority, see Understanding Transport Agents.

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The agent logs exist in C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\AgentLog.

The naming convention for the agent log files is AGENTLOGyyyymmdd-nnnn.log. The placeholders represent the following information:

  • The placeholder yyyymmdd is the Coordinated Universal Time (UTC) date that the log file was created. The placeholder yyyy = year, mm = month, and dd = day.

  • The placeholder nnnn is an instance number that starts at the value of 1 for each day.

Information is written to the log file until the file size reaches 10 MB. Then, a new log file that has an incremented instance number is opened. This process is repeated throughout the day. Circular logging deletes the oldest log files when the agent log directory reaches 250 MB, or when a log file is 30 days old.

The agent log files are text files that contain data in the comma-separated value file (CSV) format. Each agent log file has a header that contains the following information:

  • #Software   Name of the software that created the agent log file. Typically, the value is Microsoft Exchange Server.

  • #Version   Version number of the software that created the agent log file. Currently, the value is 8.0.0.0.

  • #Log-Type   Log type value, which is Agent Log.

  • #Date   UTC date-time when the log file was created. The UTC date-time is represented in the ISO 8601 date-time format: yyyy-mm-ddThh:mm:ss.fffZ, where yyyy = year, mm = month, dd = day, hh = hour, mm = minute, ss = second, fff = fractions of a second, and Z signifies Zulu, which is another way to denote UTC.

  • #Fields   Comma delimited field names used in the agent log files.

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The agent log stores each agent transaction on a single line in the log. The information stored on each line is organized by fields. These fields are separated by commas. The field name is generally descriptive enough to determine the type of information it contains. However, some of the fields may be blank. Or the type of information stored in the field may change based on the agent or the action performed on the message by the agent. The following table describes the fields used to classify each agent transaction.

Fields used to classify each agent transaction

Field name Description

Timestamp

UTC date-time of the agent event. This is represented in the ISO 8601 format. The value is formatted as yyyy-mm-ddThh:mm:ss.fffZ, where yyyy = year, mm = month, dd = day, hh = hour, mm = minute, ss = second, fff = fractions of a second, and Z signifies Zulu, which is another way to denote UTC.

SessionId

Unique SMTP session identifier. This identifier is represented as a 16-digit hexadecimal number.

LocalEndpoint

Local IP address and port number that accepted the message. SMTP sessions typically use port 25.

RemoteEndpoint

IP address and port number of the previous SMTP server that connected to this server to deliver the message. In an Edge Transport server and Hub Transport server topology, the value of RemoteEndpoint in the agent log on the Hub Transport server will be the IP address of the Edge Transport server. Even though the message is transmitted by SMTP, the port number used by the sending server will be a random number larger than 1,024.

EnteredOrgFromIP

IP address of the remote SMTP server that first connected to the Exchange organization to deliver the message. On an Edge Transport server, the value of RemoteEndpoint and EnteredOrgFromIP are the same. Anti-spam agents use the IP address in EnteredOrgFromIP to examine a message.

MessageId

Value of the MessageID header field. If this value is blank, the Exchange 2010 transport server assigns an arbitrary value, but only if the message is accepted. After assigned, the value of MessageID is constant for the lifetime of the message.

P1FromAddress

Sender e-mail address specified in MAIL FROM in the message envelope. This value is used to transport the message between SMTP messaging servers. This value serves as a comparison to the value of P2FromAddresses to determine whether the sender address in the message header is forged.

P2FromAddresses

Sender e-mail address specified in the From header field or in the Sender header field in the message header.

Recipient

E-mail address of the recipients. Although the original message may contain multiple recipients, only one recipient is displayed per line in the agent log.

NumRecipients

Total number of recipients in the original message.

Agent

Name of the agent that took the action. The possible values are as follows:

  • Connection Filter agent

  • Content Filter agent

  • Edge Rules agent

  • Recipient Filter agent

  • Sender Filter agent

  • Sender ID agent

Event

SMTP event where the action was taken by the agent. The value of Event depends on the agent. The SMTP events available to each agent are described in the first table earlier in this topic. The possible values for Event are as follows:

  • OnConnect

  • OnEndOfHeaders

  • OnEndOfData

  • OnMailCommand

  • OnRcptCommand

Action

Action performed on the message by the agent. The possible values for Action are as follows:

  • AcceptMessage

  • DeleteMessage

  • DeleteRecipients

  • Disconnect

  • QuarantineMessage

  • QuarantineRecipients

  • RejectAuthentication

  • RejectCommand

  • RejectConnection

  • RejectMessage

  • RejectRecipients

SmtpResponse

Enhanced SMTP response as defined in RFC 2034.

Reason

Reason for the action supplied by the agent.

ReasonData

Descriptive details for the action supplied by the agent.

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You can use the Get-AgentLog cmdlet in the Exchange Management Shell and the Get-AntiSpamFilteringReport script to search the agent logs. For more information, see Get-AgentLog.

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By default, agent logging is enabled on a Hub Transport server or an Edge Transport server. Agent logging is enabled or disabled by modifying the EdgeTransport.exe.config file located in C:\Program Files\Microsoft\Exchange Server\V14\Bin. For more information, see Understanding the EdgeTransport.exe.Config File. EdgeTransport.exe and MSExchangeTransport.exe are the executable files used by the Microsoft Exchange Transport service.

Many available configuration options are unrelated to agent logging. Any configuration options that don't involve agent logging are outside the scope of this topic.

  1. Open the following file by using Notepad: C:\Program Files\Microsoft\Exchange Server\V14\Bin\EdgeTransport.exe.config

  2. Modify the following line in the <appSettings> section.

    <add key="AgentLogEnabled" value="<TRUE | FALSE>" />
    

    This example disables agent logging by modifying the AgentLogEnabled parameter.

    <add key="AgentLogEnabled" value="FALSE" />
    
  3. Save and close the EdgeTransport.exe.config file.

  4. Restart the Microsoft Exchange Transport service.

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