Outlook 2003 is listed as a supported client for Exchange 2010 with the following caveats:
- Clients running Outlook 2003 don’t use RPC encryption, which RPC Client Access requires by default. You will either need to turn off the RPC encryption requirement or configure Outlook 2003 to use RPC encryption. However, Outlook 2007 and later versions are automatically compatible with the change to RPC Client Access because they support RPC encryption by default. For more information, see Understanding RPC Client Access.
- On clients running Outlook 2003, you may notice that folder updates don’t occur automatically in a timely manner. This situation occurs because User Datagram Protocol (UDP) notifications aren’t supported in Exchange 2010. For more information about resolving this issue, see Knowledge Base article 2009942, In Outlook 2003, e-mail messages take a long time to send and receive when you use an Exchange 2010 mailbox. However, Outlook 2007 and Outlook 2010 are automatically compatible with this change.
Having now witnessed the impact of the second issue it could cause you a big issue if you are running Outlook 2003 in Terminal Services or Citrix. The KB article 2008842 suggests two options:
- Make a registry interval to reduce the polling time from 60 seconds to a lower value, 10 is the minimum
- Use Outlook’s Cached Exchange mode
Having made the registry change down to 10 seconds the phrase from above ‘…..folder updates do not occur in a timely manner’ is pretty diplomatic! I think most people could live with an email sitting in the Outbox for a few seconds or being delivered within seconds rather than instantaneously. However, deleting an email and it then not dissapearing for up to 10 seconds is a real issue. It feels like it didn’t work, so naturally you press the delete key again and this time you are presented with an error because that item no longer exists. The whole experience with this refresh issue is pretty poor.
Whilst Outlook’s Cached Exchange mode is a very common deployment method for laptops and desktops (if not the standard these days) you cannot use it when running Outlook 2003 in Terminal Services or Citrix.
The final option is an upgrade to Outlook 2007 / 2010 which might not be a big deal in some organisations, in others it will involve significant work and planning.
It appears that there is unlikely to be a better fix either. Further details already written up very well here.
The KB article has been updated to reflect the fact that the minimum value can actually be set to 5 seconds not 10. Whether that is an acceptable value for your environment is another matter.
So it looks like enough customer pressure has been placed and the Exchange Team have just announced that UDP support for Outlook 2003 will be available for Exchange 2010 in Roll-up 3 for SP1. This means you can now consider Outlook 2003 in Terminal Services as a viable client for Exchange 2010 again.