Exchange EWS SearchMailboxes invalid child element error - exchange-server

Question

I have a strange error. When i try to do a SearchMailboxes, I get this error:
Unhandled Exception: Microsoft.Exchange.WebServices.Data.ServiceResponseException: The request "://schemas.microsoft.com/exchange/services/2006/types" has invalid child element 'ExtendedAttributes'
The problem is that i get this error in some pc's. With fiddler I could see that my pc sends a request without the node ExtendedAttributes and it works.
This is the ExtendedAttributes node that produces the error.
The code:
List<MailboxSearchScope> scopeList = new List<MailboxSearchScope>();
foreach (SearchableMailbox mb in searchableMailboxes)
{
MailboxSearchScope scope = new MailboxSearchScope(mb.ReferenceId, MailboxSearchLocation.All);
scopeList.Add(scope);
}
MailboxQuery query = new MailboxQuery(searchQuery, scopeList.ToArray());
MailboxQuery[] mbQueryList = new MailboxQuery[] { query };
SearchMailboxesParameters p = new SearchMailboxesParameters
{
SearchQueries = mbQueryList,
ResultType = SearchResultType.PreviewOnly
};
ServiceResponseCollection<SearchMailboxesResponse> res = _service.SearchMailboxes(p);

Answer 1

ExtendedAttributes is a new element that was introduced in Exchange 2013 SP1 and is intended for internal use only.
http://msdn.microsoft.com/en-us/library/office/dn627392(v=exchg.150).aspx
I don't see in your code where you are trying to use this element so I would suggest that you specify ExchangeVersion.Exchange2013 when you are instantiating your ExchangeService object.