Exchange Web Services as a replacement to MAPI?

Exchange Web Services (EWS) provides the functionality to enable client applications to communicate with the Exchange server. EWS provides access to much of the same data that is made available through Microsoft Office Outlook. EWS clients can integrate Outlook data into Line-of-Business (LOB) applications. SOAP provides the messaging framework for messages sent between the client application and the Exchange server. The SOAP messages are sent by HTTP.

EWS is described by three files:

Services.wsdl   Describes the contract between client and server.
Messages.xsd   Defines the request and response SOAP messages.
Types.xsd   Defines the elements used in the SOAP messages.
These schema files are located in the IIS virtual directory that hosts Exchange Web Services of the computer that is running Microsoft Exchange Server that has the Client Access server role installed.

EWS provides the following types of operations:

Availability
Bulk Transfer (new in Exchange 2010)
Conversations (new in Exchange 2010)
Delegate Management
Exchange Store Search
Exchange Search (new in Exchange 2010)
Federated Sharing (new in Exchange 2010)
Folder
Inbox Rules (new in Exchange 2010)
Item
Mail Tips (new in Exchange 2010)
Messaging Records Management
Message Tracking (new in Exchange 2010)
Notification
Service Configuration (new in Exchange 2010)
Synchronization
Unified Messaging (new in Exchange 2010)
User Configuration (new in Exchange 2010)
Utility

The Availability operations improve information workers' calendar and free/busy sharing experience by providing secure, up-to-date, and rich free/busy information. This information enables developers to create sophisticated collaboration and scheduling applications.

The Availability Web service provides tools to create enhanced Exchange Server 2010 client applications by doing the following:

Retrieving live free/busy information for Exchange 2010 mailboxes.
Retrieving live free/busy information from other Exchange 2010 forests.
Retrieving published free/busy information from public folders.
Retrieving suggested meeting times.
Supplying up-to-date free/busy data so that users and resources can be scheduled with more confidence.
Supplying more specific data that describes the status of users and resources, such as the start times and the end times of individual appointments, subjects, locations, work hours, and so on.
Securing the distribution of free/busy data by specifying the level of detail to share with specified users.
In addition, the Availability operations enable the user to share their calendar information in more granular ways. For each target person/group, the user can select one of four levels of sharing:

Share nothing
Share their free/busy information
Share more detail including subject, location, and timing
Share full calendar details

The Availability operations improve information workers' calendar and free/busy sharing experience by providing secure, up-to-date, and rich free/busy information. This information enables developers to create sophisticated collaboration and scheduling applications.

The Availability Web service provides tools to create enhanced Exchange Server 2010 client applications by doing the following:

Retrieving live free/busy information for Exchange 2010 mailboxes.
Retrieving live free/busy information from other Exchange 2010 forests.
Retrieving published free/busy information from public folders.
Retrieving suggested meeting times.
Supplying up-to-date free/busy data so that users and resources can be scheduled with more confidence.
Supplying more specific data that describes the status of users and resources, such as the start times and the end times of individual appointments, subjects, locations, work hours, and so on.
Securing the distribution of free/busy data by specifying the level of detail to share with specified users.
In addition, the Availability operations enable the user to share their calendar information in more granular ways. For each target person/group, the user can select one of four levels of sharing:

Share nothing
Share their free/busy information
Share more detail including subject, location, and timing
Share full calendar details

Thanks guys!

So basically EWS is a replacement for WebDav? It's in no way a replacememt for MAPI since it can't do most things that MAPI does?

I searched on the MS site but can't find a comparison of the most general tasks that MAPI can do that EWS can't...does anyone have a handy link or know this info? Just the generics will help me!

Thanks so much.

Exchange 2007 had both WebDAV and EWS in 2010 since webdav was removed all 3rd party applications are now moving towards EWS