I have followed the instructions and have tasks succesfully syncing to my Outlook clients, however nothing I do in my Outlook client will sync back to the Project Server.
A notification for subscription [FwBleDEucml2ZXJwb2ludGZhcm1zLmNvbRAAAAAq87PT4kkHR7LK5S8EHY5glaEFvp9NzQg=] against endpoint [http://portal.domain.com/PWA/_vti_bin/PSI/ExchangeSync.asmx] couldn't be sent. (Send attempts: 7) Details: WebException: The remote
server returned an error: (500) Internal Server Error. StatusCode: InternalServerError Internal Server Error at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at Microsoft.Exchange.Services.Core.NotificationServiceClient.HandleResponse(IAsyncResult responseAsyncResult)