Exchange Web Services, WebDAV & MAPI


I have been reading up on Exchange 2010 and the new Exchange Web Services, but there seems to be a lot of confusion.

According to Wiki ( )

"Exchange Web Services (EWS), an alternative to the MAPI protocol, is a documented SOAP based protocol introduced with Exchange Server 2007 which significantly reduces synchronization time between the server vs. WebDAV, which is used by Exchange Server 2003"

On one hand it is saying that EWS is the replacement to MAPI, on the other it is implying that EWS is the successor to WebDav.

Can anyone expand? What is the primary point of EWS -

a) As some sort of long term replacement to MAPI?
b) A replacement for WebDav
c) A method for non-MS products to connect to Exchange mailboxes

Would be grateful if someone could clear this up! If, indeed, it is a long term replacement for MAPI, does that indicate that MS will move Outlook (fat client) away from MAPI and towards EWS in the future?
Who is Participating?
endital1097Connect With a Mentor Commented:
a) ews is not the replacement of mapi. the rpc client access service that runs on the cas server takes the mapi connections away from the mailbox server

b) ews is the replacement for webdav

c) yes, it allows developers to write custom applications to interface with exchange (access to user mailboxes, calendars, etc)
tomd1976Author Commented:
Thanks endital1097, so EWS does not have the full functionality of MAPI yet?

Do you know what it's missing, I have searched the web for what seems like an eternity and can't find something that outlines the differences.
It isn't a protocol like mapi
Ewa is just an interface into exchange
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tomd1976Author Commented:
Sure, but what's the difference in real terms? MAPI will always be around and can co-exist with EWS?
i wouldn't be surprised to see MAPI be replaced by EWS, but i have not heard any roadmap
until then they will coexist
sunnyc7Connect With a Mentor Commented:
My $0.02 apart from what endital has already added.

MAPI is a hold-over from the DLL generation. MAPI uses providers, which are DLL's doing a specific work.  Any client software which uses MAPI to communicate with exchange can be called a MAPI client. All Outlook versions are MAPI clients.

EWS is more web-services and SOAP based
Before EWS was released, exchange services were all strung together with different technologies, web-dav, Exchange SDK etc. Exchange EWS provides one uniform layer to access all services of exchange. You can write your code in any language, and call exchange components anywhere using SOAP/WSDL communication with EWS.

Here's a list of features that you access through EWS

To answer your question
a) EWS as a replacement to MAPI?
>> No. I dont think so. MAPI will rule the world in Outlook client side, EWS will rule on web + integrating with various apps. The whole world is invested in MAPI way too much to move away from it

b) A replacement for WebDav
>> Yes. EWS will definitely replace webdav.

c) A method for non-MS products to connect to Exchange mailboxesion:
>> Exactly. using EWS you can can do that.

An example here

Here's a similar discussion at EE

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