Question about Outlook Express

(Mac issue starts in paragraph 6 but the background is important, since I think these problems are related.)

My company is a SaaS provider with more than 1000 customers. We are using a hosted Exchange 2010 system provided by a 3rd party. In addition to separate email accounts for each employee, we also have a "Support@" mailbox into which all email correspondence with our customers in received and stored. This account has a large folder tree with more than 1500 folders (including archives for customers who are no longer using our service.) The overall size is about 4GB and 100,000+ messages.

We have two support people who both have their own email accounts and who also are supposed to have access to the Support@ account so that they can respond to customer support requests, then create folders (for a new customer) and move messages around. The Support Inbox is generally empty since we handle all emails as soon as they arrive.

One support person is using Outlook 2010 - he has two Exchange accounts configured. The other is using Outlook 2007. She has the Support account configured as an "Additional mailbox to open" when she starts Outlook (since 2007 apparently doesn't support 2 Exchange accounts.) Both of these employees are configured in Exchange to have "Full Access" and "Send As" permissions. Within Outlook, both employees are also configured as "Owners" of the Support mailbox.

The problem we are having is that this is not working. The two employees can see the Support mailbox but they don't have full access to it. For the guy using Outlook 2010, his system started to synchronize but then stopped about 10% in and won't continue. For the gal using Outlook 2007, she can see most of the tree. But if I create a new folder, she doesn't see it and she can't move messages into folders.

For both employees, if they use Outlook Web Access, everything works correctly. They can move messages around and see them immediately. So this strongly suggests that security is correctly configured in Exchange, and that this is an Outlook problem on their local computers.

Now, I'm having a slightly different problem. I run Outlook 2011 on a Mac. I also have Full Access/Owner rights to the Support mailbox. I can see the full tree; I can create folders and move messages around with no problems. However, approx. every 1-2 minutes, I get a Mac beach ball (equivalent of the Windows hourglass) and everything locks up for about 10 seconds. Then I can keep working. Of course, the Mac uses individual files for each messages, instead of a monolithic PST file; not sure why this would matter...

Our email hosting company is now trying to tell us that the problem is we have too many folders and there is a limit of 500 folders. This doesn't make sense. These problems actually started about 4 weeks ago after they did some reconfiguration work on their servers. Before then, we had basically the same number of folders and messages and were not having this problem (maybe we added 10 folders since then; lots of messages though.)

We're at our wits end with this. This is our whole support operation and our support team need to be able to access folders and messages. I think this is some kind of synchronization problem. Any suggestions would be greatly appreciated.

I will cross-post this request in the Outlook Forums as well, since it may be an Outlook issue.

Dan