Outlook 2003 Client connections fail after a while, requiring reboot

Question

I have Windows 2003 Server terminal servers in several sites, with Outlook 2003 as email clients.  Server is Exchange 2010, located in my main site.  The remote site terminal servers are connected through WAN links that are 5 Mbps connections,
with generally very low usage compared to capacity.
Outlook works properly for 2 - 3 days for the remote site users, but then, their connections start to drop, and they see "Outlook is trying to connect the the exchange server ..." systray messages, and they lose their email.  Can't see their
inbox contents,  though sometimes the tree gets populated.  The only fix is to reboot the terminal server. 
Similar terminal servers at the main site do not experience this.
The backstory is that I recently migrated users from Exchange2003 to Exchange2010.  On exchange 2003 we never had this problem.
What is going on here?

Answer 1

Hi,
From your description, I would like to clarify the following things:
1. Make sure that these problematic users use Microsoft Office Outlook 2003 Service Pack 2 or later version.
2. The default Exchange Server 2010 RTM configuration requires RPC encryption. However, Microsoft Office Outlook 2003 does not use RPC encryption by default. You need to update an existing Outlook 2003 profile manually so that it uses RPC encryption with
Exchange 2010.
For more information about it, here is a helpful KB for your reference.
Outlook connection issues with Exchange 2010 mailboxes because of the RPC encryption requirement
https://support.microsoft.com/kb/2006508?wa=wsignin1.0
Hope this can be helpful to you.
Best regards,
Amy Wang
TechNet Community Support