I have a user who reported that when opening or previewing (in reading pane) an email, Outlook will hang for several minutes or sometimes crash.

Upon investigating I found that the offending emails had something in common. While the vast majority (~95%) of emails have the message class IPM.Note, the emails that are causing this problem are the ones that have a different message class. Doesn't seem to matter which it is, as long as it's not IPM.Note.

In testing this I tried checking the connection status (Ctrl-Click systray Icon). When I try to open one of those emails I see Outlook starts trying to connect to 3 or 4 different servers in turn (none of which are the server for that mailbox). It will try this for anywhere from 5-10 minutes and if Outlook doesn't crash in the process, eventually it will give up trying to connect to anything and the email will open just fine.

This is quite the stumper.

Windows 7
Outlook 2010
Connected to exchange through proxy server