A major factor in moving from Outlook 2000 to Outlook 2003 was the advantage of utilizing RPC calls to make connections from Outlook clients to an Exchange server. The specific technology for making these internet connections was RPC over HTTP.  RPC means remote procedure calls and allow your Outlook MAPI clients to connect to Exchange servers using HTTP or the secure HTTPS protocol.

Remote Procedure Call (RPC) is a protocol that one application can use to request a service from another application running in another system in a network without having to understand network details. Remote Procedure Calls uses the client/server model. The requesting application is a client and the application which supplies the service is the server component. Remote Procedure Calls are synchronous operations that require the requesting application to wait until the results of the remote procedure are returned from the server. The uses of lightweight processes or threads that share the same address space allow multiple Remote Procedure Calls to be performed concurrently.

One of the advantages of using RPC over HTTP is that this methodology can support secure connections to the Exchange server and thus add an additional layer of security between the client and the server.

The other benefit is that these RPC commands could be encapsulated in HTTP. What this means from an administrator perspective is that only one of two ports would need to be opened at the firewall – port 443 or port 80 – as opposed to earlier versions which would have required two additional ports: port 135 and port 53. These ports were well known to hackers and used by them to create havoc within many organizations on a routine basis.

Continue reading Troubleshooting Connections to Exchange Server using HTTP

More and more companies are allowing employees to work from home via remote offices. Outfitted with high-speed internet, separate phone lines for fax and business calls and office white boards and most office workers are ready to be productive as if they were working in any office environment complete with interruptions – though not the usual kind.

One of the interruptions remote office employees will most often face is that of remote connectivity problems. The problem of a remote connection being down is that it is sometimes hard to pinpoint the exact cause of the remote connectivity issue.

For instance, users have reported remote connectivity problems when running Exchange 2003 on a Windows 2003 Enterprise Server. Remote users will experience “disconnected” status issues when connected remotely and Outlook will be displayed as being in “offline” mode. However, when users are in their company’s office they do not have any problems connecting to their Exchange mailbox while using Outlook 2007. And running in cached exchange mode does not appear to help either.

One of the first steps that an administrator should perform is to verify whether the Virtual Private Network (VPN) is working correctly or whether it is part of the problem. An administrator can bypass the VPN by configuring Outlook to communicate with the Exchange server via Remote Procedure Calls (RPC) over Hyper Text Transfer Protocol (HTTP). This will allow the administrator to confirm whether the remote communication problem still exists even when not using a VPN connection. If there is still a remote connection issue, while running RPC over HTTP, then the administrator will know that VPN is not part of the problem.

Continue reading Troubleshooting Unavailable Exchange Server