Exchange Web Services (EWS) is a robust API that exposes many Exchange client access features. Many popular clients use this API on many different platforms. What if you want to limit client access via EWS, however? You do have an option. In Exchange 2010, you can use the Set-CASMailbox command to modify EWS access.

Note:   The Set-CASMailbox command in Exchange 2007 does not provide options for limiting EWS access.

The following options that the Set-CASMailbox command exposes enable you to change the settings on a per-user basis:

• Turn EWS on/off
• Turn EWS on/off for Outlook, Mac Outlook, and Entourage
• Turn EWS on/off using allow/block lists for user agent filtering

These options make use of the user agent header to filter access. While useful in many scenarios, user agent filtering has one  inherent disadvantage: User agent strings can easily be written to represent agents on an allowed list, including Outlook, Mac Outlook, and Entourage. Of equal importance is the fact that specific EWS features can’t be blocked. EWS feature access is not segmented to allow access to particular EWS operations — it’s all or nothing. Turning off EWS will affect clients that use the OOF settings, availability, mail tips, and so on. It is important to take this into consideration when planning the client-server interaction part of your system architecture.

UPDATE: 8 November 2011, Thom Randolph - MSFT.

The following API reference information in this post applies to the Windows Extensible Storage Engine (ESE) APIs, that are available on MSDN at the following URL:

http://msdn.microsoft.com/en-us/library/windows/desktop/gg269259(v=EXCHG.10).aspx

The ESE APIs that ship in Windows should not be used with Exchange mailbox or public folder databases.

The JET_ERRINFOBASIC_W API includes a group of constants, a structure, and a function, as defined in the header file Esent.h. These are described in this blog post.

Note: This documentation is based on a preliminary release of the Extensible Storage Engine. This information is subject to change.

JET_ERRCAT Constants

The JET_ERRCAT group of constants describes higher-level classifications or categories of errors. This group of constants enables applications to define default treatment for a classification of errors, rather than handling each error case individually. It also ensures that the application does not have to handle new error conditions that are included in existing classifications.

The JET_ERRCAT constants are arranged in a specific hierarchy of conditions and subconditions, as follows:

|--- Error
|--- Operation(al)
| |--- Fatal
| |--- IO
| |--- Resource
| |--- Memory
| |--- Quota
| |--- Disk
|
|--- Data
| |--- Corruption
| |--- Inconsistent
| |--- Fragmentation
|
|--- Api
|--- Usage
|--- State

The following table lists the JET_ERRCAT constants and provides a description and recovery information, as applicable.

Requirements

JET_ERRINFOBASIC_W Structure

The JET_ERRINFOBASIC_W structure defines the data that is returned from the JetGetErrorInfo() method when the JET_ErrorInfoSpecificErr InfoLevel [LG1] is passed in.

typedef struct {
         unsigned long    cbStruct;
         JET_ERR          errValue;
         JET_ERRCAT       errcatMostSpecific;
         unsigned char    rgCategoricalHierarchy[8];
         unsigned long    lSourceLine;
         WCHAR            rgszSourceFile[64];
} JET_ERRINFOBASIC_W;

Members

cbStruct
The size of the structure, in bytes. It must be set to sizeof( JET_ERRINFOBASIC ).

errValue
The error value that was evaluated, as passed in for the pvResult argument to JetGetErrorInfo().

errcatMostSpecific
The lowest-level JET_errcat constant that is associated with the error; that is, the leaf-level category in the category hierarchy documented in JET_ERRCAT.

rgCategoricalHierarchy[8]
The hierarchy of error categories that is associated with the error. Position 0 is the highest level in the hierarchy of JET_ERRCAT, and the rest are subcategories until the most specific category is set, after which all categories are JET_errcatUnknown.

lSourceLine
Reserved.

rgszSourceFile[64]
Reserved.

Requirements

JetGetErrorInfoW Function

The JetGetErrorInfoW function BAS_ of the database engine.

JET_ERR JET_API JetGetErrorInfoW(
         _In_opt_ void *                    pvContext,
         _Out_writes_bytes_( cbMax ) void * pvResult,
         _In_ unsigned long                 cbMax,
         _In_ unsigned long                 InfoLevel,
         _In_ JET_GRBIT                     grbit );

Parameters

pvContext
The context or error value for which the extended error information is needed. The value passed in depends on the InfoLevel parameter value.

pvResult
A pointer to a buffer that will receive the information. The type of the buffer depends on the InfoLevel parameter value. The caller must be configured to align the buffer appropriately.

cbMax
The maximum size of the pvResult structure that is passed in.

InfoLevel
The type of information that will be retrieved for the error info/context is specified by the pvContext parameter. The format of the data that is stored in pvResult is dependent on InfoLevel.

The following table lists the possible values for this parameter.

grbit
Reserved.

Return Value

This function returns the JET_ERR data type with one of the return codes listed in the following table. For more information about the possible ESE errors, see Extensible Storage Engine Errors and Error Handling Parameters.

On success, the output buffer that is appropriate for the requested error context/value will be set to the extended error info requested.

On failure, the state of the output buffers will be undefined.

Remarks

The JET_ERRINFOBASIC_W function and JET_ERRCAT group of constants contain documentation about the extended error information that is returned for InfoLevel = JET_ErrorInfoSpecificErr.

Requirements