RTM Exchange 2007 gives you WebSevices and PowerShell.  The link below covers this. 

 

  Technical Articles 2007

  http://msdn2.microsoft.com/en-us/library/bb738396(EXCHG.80).aspx

 

With Exchange 2007 SP1 you get a lot of cool new things which go way past the limitations of what the RTM could do.  Below is a summary of things you need to be aware of for development.

 

     You can create & register custom ASP forms based on a custom message type and operation performed on that item.  Premium OWA UI – not basic.

     You can do some customization of the OWA UI.   Premium OWA UI – not basic.

     You can work with Delegates using EWS.

     You can work with Public Folders using EWS.

     You can work with folder security settings using EWS.

     You can do id conversions between PR_EntryID, EWS  identifier OWA identifier, etc.  So, now you can “get there from here”.

 

Note:  There is no API for working with OWA settings and WebDAV cannot be used in any supported way in this area.  Same is true for the RTM version.  Applications which used WebDAV to work with OWA settings will likely fail under the RTM and SP1 versions of Exchange SP1.

 

Suggested reading for EVERYONE:

 

- http://technet.microsoft.com/en-us/library/bb676323(EXCHG.80).aspx  - What's New in Exchange Server 2007 SP1

- http://msdn2.microsoft.com/en-us/library/bb856575(EXCHG.80).aspx   - Adding Delegates (Exchange Web Services)

- http://msdn2.microsoft.com/en-us/library/bb856532(EXCHG.80).aspx  - Setting Folder-Level Permissions (Exchange Web Services)

- http://technet.microsoft.com/en-us/library/bb676323.aspx - Whats new in Exchange server 2007 SP1
- http://msdn2.microsoft.com/en-us/library/bb891801.aspx  - Customizing Outlook Web Access
-
http://msdn2.microsoft.com/en-us/library/bb891803.aspx  - Introduction to OWA customization

- http://msdn2.microsoft.com/en-us/library/bb891879.aspx  - OWA forms registry

- http://msdn2.microsoft.com/en-us/library/bb891846(EXCHG.80).aspx    - Outlook Web Access User Interface Customization XML Elements

- http://msdn2.microsoft.com/en-us/library/bb856559.aspx   - Converting Identifiers (Exchange Web Services)