I am responsible for a Microsoft Small Business Server 2003 serving e-mail via Exchange to a small company.
Yesterday, it appears everything was working fine. This morning, one account (the one that is used most intensively, of course) started to act "weird":
In Outlook 2010, no new e-mails appear in the Inbox. E-Mails that are (via automatic rules) being delivered to subfolders of Inbox, however, appear fine. Outlook says "all folders are up to date".
On iOS devices, it's pretty much the same picture: Subfolders of Inbox work fine, Inbox itself does not update. However, it appears that the process to fetch new e-mails in Inbox takes a long time and eventually says "the connection to the server failed".
Outlook Web Access, however, shows all e-mails (in the Inbox as well as in subfolders of Inbox)
While testing, I logged into this account from a computer that has never been logged in before, and started Outlook. It downloaded the content of all folders in a way that appears correct, except Inbox which appears totally empty. Subfolders of Inbox, again, work fine.
Sending e-mail appears to work fine.
All other accounts on the same server appear to work fine.
The event log on the server shows lots of those errors:
Source: Server ActiveSync Type: Error Event ID: 3005
Unexpected Exchange mailbox Server error: Server: [servername] User: [affected_username] HTTP status code: [400]. Verify that the Exchange maibox Server is working correctly.
The web server log shows the offending requests are
SEARCH /exchange-oma/[affected_username]/
and that indeed a status code of 400 is returned
The folder size of Inbox (without subfolders), as shown from the "folder properties", on the server, is shown as 5'669'022 kB.
Is it possible that this is "too big to handle", and all of the symptoms I'm seeing are a result of this?
So, there was not really a "simple" solution. The exact details stay unresolved.
What we did, was setting up a new Exchange 2010 Server on a new machine (and, for good measure, an additional domain controller on yet another new machine), and then move the mailboxes from the Small Business Server to the Exchange 2010.
When we got to the problematic mailbox, it refused to move with the following message:
We took this as the final evidence that there is really something very wrong with that mailbox. So we deleted it on the old server, created a new one, and are now copying back all the needed mails, calendar entries, contacts, notes and todo items from Outlook.