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Understanding Mailbox Audit Logging

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

Because mailboxes can potentially contain sensitive, high business impact (HBI) information and personally identifiable information (PII), it's important that you track who logs on to the mailboxes in your organization and what actions are taken. It's especially important to track access to mailboxes by users other than the mailbox owner. These users are referred to as delegate users.

By using mailbox audit logging, you can log mailbox access by mailbox owners, administrators, and delegates (including administrators who have full mailbox access permissions). Mailboxes are considered to be accessed by an administrator only in the following scenarios:

When you enable audit logging for a mailbox, you can specify which user actions (for example, accessing, moving, or deleting a message) should be logged for a logon type (administrator, delegate user, or owner). The audit log entries also include important information, such as the client IP address, host name, and the process or client that is used to access the mailbox. For items that are moved, the entry includes the name of the destination folder.

Note

For mailboxes such as the Discovery Search Mailbox, which may contain more sensitive information, consider enabling mailbox audit logging for mailbox owner actions such as message deletion.

Contents

Mailbox Audit Logs

Enabling Mailbox Audit Logging

Searching Mailbox Audit Log Entries

Mailbox Audit Log Entries

Mailbox Audit Logs

Mailbox audit logs are generated for each mailbox that has mailbox audit logging enabled. Log entries are stored in the Audits subfolder of the audited mailbox Recoverable Items folder. This ensures that all audit logs are available from a single location, regardless of which client access method was used to access the mailbox or which server or workstation an administrator used to access the mailbox audit log. If you move a mailbox to another Mailbox server, the mailbox audit logs for that mailbox are also moved because they're located in the mailbox.

By default, mailbox audit log entries are retained in the mailbox for 90 days and then deleted. You can modify this retention period by using the AuditLogAgeLimit parameter together with the Set-Mailbox cmdlet. If a mailbox is on litigation hold, audit log entries are only retained until the audit log retention period for the mailbox is reached. To retain audit log entries longer, you have to increase the retention period by changing the value for the AuditLogAgeLimit parameter, or export audit log entries before the retention period is reached. For more information, see Create a Mailbox Audit Log Search.

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Enabling Mailbox Audit Logging

Mailbox audit logging is enabled per mailbox. Use the Set-Mailbox cmdlet to enable or disable mailbox audit logging. For details, see Enable or Disable Mailbox Audit Logging for a Mailbox.

When you enable mailbox audit logging for a mailbox, access to the mailbox and certain administrator and delegate actions are logged by default. To log actions taken by the mailbox owner, you must specify which owner actions should be audited. The following table lists the actions logged by mailbox audit logging, including the logon types for which the action is logged.

Mailbox actions logged by mailbox audit logging

Action Description Administrator Delegate Owner

Copy

An item is copied to another folder.

Yes

No

No

Create

An item is created in the mailbox. (For example, a message is sent or received.)

Note

Folder creation isn't audited.

Yes*

Yes*

Yes

FolderBind

A mailbox folder is accessed.***

Yes*

Yes**

No

HardDelete

An item is deleted permanently from the Recoverable Items folder.

Yes*

Yes*

Yes

MessageBind

An item is accessed in the reading pane or opened.***

Yes

No

No

Move

An item is moved to another folder.

Yes*

Yes

Yes

MoveToDeletedItems

An item is moved to the Deleted Items folder.

Yes*

Yes

Yes

SendAs

A message is sent using Send As permissions.

Yes*

Yes*

Not applicable

SendOnBehalf

A message is sent using Send on Behalf permissions.

Yes*

Yes

Not applicable

SoftDelete

An item is deleted from the Deleted Items folder.

Yes*

Yes*

Yes

Update

An item's properties are updated.

Yes*

Yes*

Yes

* Audited by default if auditing is enabled for a mailbox. ** Entries for folder bind actions that are performed by delegates are consolidated. One log entry is generated for individual folder access within a time span of twenty-four hours. *** FolderBind and MessageBind are not logged for the default calendar.

Mailbox access by authorized automated processes, such as accounts used by third-party tools or accounts used for lawful monitoring, can create a large number of mailbox audit log entries. This may not be of interest to your organization. You can configure such accounts to bypass mailbox audit logging. For details, see Bypass a User Account From Mailbox Audit Logging.

If you no longer require certain types of mailbox actions to be audited, you should modify the mailbox's audit logging configuration to disable those actions. Existing log entries aren't purged until the configured audit log age for the mailbox is reached.

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Searching Mailbox Audit Log Entries

You can use the following methods to search mailbox audit log entries:

  • Synchronously search a single mailbox   You can use the Search-MailboxAuditLog cmdlet to synchronously search mailbox audit log entries for a single mailbox. The cmdlet displays search results in the Exchange Management Shell window. For more information, see Search-MailboxAuditLog and Search the Mailbox Audit Log for a Mailbox.

  • Asynchronously search one or more mailboxes   You can create a mailbox audit log search to asynchronously search mailbox audit logs for one or more mailboxes, and then have the search results sent to a specified e-mail address. The search results are sent as an XML attachment. To create the search, use the New-MailboxAuditLogSearch cmdlet. For details, see Create a Mailbox Audit Log Search.

  • Use auditing reports in Exchange Control Panel   You can use the Auditing tab in Exchange Control Panel (ECP) to run auditing reports or export entries from the mailbox audit log and the administrator audit log. For details, see Auditing Tab.

Mailbox Audit Log Entries

The following table describes the fields logged in a mailbox audit logging entry.

Mailbox audit log fields

Field Populated with

Operation

One of the following actions:

  • Copy

  • Create

  • FolderBind

  • HardDelete

  • MessageBind

  • Move

  • MoveToDeletedItems

  • SendAs

  • SendOnBehalf

  • SoftDelete

  • Update

OperationResult

One of the following results:

  • Failed

  • PartiallySucceeded

  • Succeeded

LogonType

Logon type of the user who performed the operation. Logon types include:

  • Owner

  • Delegate

  • Admin

DestFolderId

Destination folder GUID for move operations.

DestFolderPathName

Destination folder path for move operations.

FolderId

Folder GUID.

FolderPathName

Folder path.

ClientInfoString

Details that identify which client or Exchange component performed the operation.

ClientIPAddress

Client computer IP address.

ClientMachineName

Client computer name.

ClientProcessName

Name of the client application process.

ClientVersion

Client application version.

InternalLogonType

Logon type of the user who performed the operation. Logon types include:

  • Owner

  • Delegate

  • Admin

MailboxOwnerUPN

Mailbox owner user principal name (UPN).

MailboxOwnerSid

Mailbox owner security identifier (SID).

DestMailboxOwnerUPN

Destination mailbox owner UPN, logged for cross-mailbox operations.

DestMailboxOwnerSid

Destination mailbox owner SID, logged for cross-mailbox operations.

DestMailboxOwnerGuid

Destination mailbox owner GUID.

CrossMailboxOperation

Information about whether the operation logged is a cross-mailbox operation (for example, copying or moving messages among mailboxes).

LogonUserDisplayName

Display name of user who is logged on.

DelegateUserDisplayName

Delegate user display name.

LogonUserSid

SID of user who is logged on.

SourceItems

ItemID of mailbox items on which the logged action is performed (for example, move or delete). For operations performed on a number of items, this field is returned as a collection of items.

SourceFolders

Source folder GUID.

ItemId

Item ID.

ItemSubject

Item subject.

MailboxGuid

Mailbox GUID.

MailboxResolvedOwnerName

Mailbox user resolved name in the format DOMAIN\SamAccountName.

LastAccessed

Time when the operation was performed.

Identity

Audit log entry ID.

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