Exchange Web Services - Active Directory is unavailable?

Question

Setting: Exchange Web Services (EWS), Exchange Server 2007 SP2, and an ASP.Net web application.

Problem: in the system we use EWS to send emails, sometimes we use extended properties to track more information. This module had been working fine for a long time until a couple of weeks ago, and I am not sure why or what is causing the Active Directory is unavailable error!!

The thing is that there is no pattern (or I am not able to find one so far), sometimes it works fine and sometimes I get the AD error.

I've been searching for more info about this error and didnt find much!

Answer 1

After long investigation and the help of our IT support team, the problem was with one of the Active Directory servers (not sure what was wrong with it) but all requests that went to this server gave this error, they took it down or restarted it and everything worked again