http://blogs.technet.com/b/get-exchangehelp/archive/2013/01/31/the-curious-case-of-maxconcurrentapi.aspxOne of the issues we seem to encounter more often than not with Exchange 2010 is NTLM authentication issues. Due to the architectural changes in Exchange 2010 (with all connectivity running through the Client Access servers), a high volume of NTLM trafficen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)