Glen's Exchange and Office 365 Dev Blog

The directory functionality in Exchange Web Services can be a little limited and so within Exchange 2010 without using LDAP to access Active Directory directly there is no direct way to access custom Resource properties on Meeting Rooms or where you want to access Custom Attributes. However using Custom MailTips is one way of working around this issue (although it means duplicating the information). For example to Create a Custom Mail Tip for a mailbox you use set-mailbox meetingRoom2 -MailTip "Expresso Machine" Then in EWS you can use this to retrieve the MailTip GetMailTipsType gmType =  new  GetMailTipsType();   gmType.MailTipsRequested =  new  MailTipTypes();   gmType.MailTipsRequested = MailTipTypes.CustomMailTip;   gmType.Recipients =  new  EmailAddressType[1];   EmailAddressType rcip1 =  new  EmailAddressType();   rcip1.EmailAddress...

If your developing EWS code against Exchange Online or possibly another large load balanced Hosted Exchange system you may find that a lot of the sample code you see on MSDN or other places that uses EWS Proxy code will always return 401 errors when you try to use it against Exchange Online (The Managed API isn't affected) eg a standard example is something like http://msdn.microsoft.com/en-us/library/bb408524%28v=EXCHG.140%29.aspx . What can cause this problem is the failure to process the exchangecookie in an appropriate way. There is description of what the exchangecookie is used for on http://blogs.msdn.com/b/exchangedev/archive/2011/07/20/client-access-server-affinity-and-network-load-balancing-considerations-for-programmatic-access-to-exchange-online.aspx . Although this says nothing about Authentication if the request object your using be its a SOAP proxy or HttpwebRequest doesn't have the cookiecontainer initialized (which by default they don't) before you submit ...