The upshot being:-
- You cannot specify a proxy server/credentials on a service by service basis - BAD TIMES
- You CAN tell your application to use the default credentials for any proxy server it encounters while trying to make a request.. The answer lies in the following bit of code
WebRequest.DefaultWebProxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
For VB.NET, just remove the semicolon at the end of the line and place it above where you initialise your Exchange connector. Worked a treat for me ;-)
All credit to Mr David Claux for finding this one....