failed proxy Exchange Web Services

This is the only single result that I can find that mentions your complete error message:
http://ripcordblog.blogspot.co.uk/2010/09/blackberry-internet-services-bis-and.html

Oops, found another one that mentions the same reg key:
http://ninjareboot.blogspot.co.uk/

i tried open internal url. it opens but format is not proper. Is this correct. ?
even owa/activesync directory taking   very long time to open.

Are you accessing the InternalURL for webmail of your local site or remote site?

Regards,
Exchange_Geek

i am having 2 sites. dag server in one of the  site got crashed. external web site is in cas server on same site. and now we are getting the above  message .

Client Access server CHM1 failed to proxy Exchange Web Services to Active Directory site CN=IN,CN=Sites,CN=Configuration,DC=co,DC=com because none of the Client Access servers in this site are responding. Please check the configuration and status of the servers in site CN=IN,CN=Sites,CN=Configuration,DC=co,DC=com.

even mail flow is very slow..

@Vijaygotur:

You have CAS Server in each site (that's evident from your post).

What I am asking is simple, check webmail for internal users (that data would be visible in EMC), you'll need to place the URL in IE and enter credentials for any mailbox that is now hosted on SiteB.

Which part of this query sounds tough to impliment?

Regards,
Exchange_Geek

webmail for internal users works fine.  

I am getting above error at 2-3 times in a hour.

If it is only 2-3 times in an hour, avoid the hassle to troubleshoot so much, it may be a network packet getting dropped between the sites.

Regards,
Exchange_Geek

What would you suggest if it  is repeatedly throwing same error ?

I wouldn't bother if it is throwing the same error once an hour or so and my webmail access works across sites (that's what you wrote)

Regards,
Exchange_Geek