I started a small (4 user) 365 migration yesterday afternoon, from Exchange 5.5.
I used the Outlook client to upload the data (export to/from PST).
There are about three shared mailboxes, and a couple of users have delegated accessed (FullAccess) to some of the other user's mailboxes.
The mail import has completed over night, but still, when I click on to one of the non-cached (for now) shared mailboxes, Outlook hangs for ages (minutes, not responding), followed by "the connection to the Exchange server is unavailable).
There is an hourglass on the Outlook icon in the system tray.
Sometimes if I close Outlook and try again, it is OK. I had the same delays adding the shared mailboxes into the "Open these additional mailboxes" exchange account properties in Outlook.
This is Outlook 2010 SP1 32-bit on Windows XP SP3.
Fresh Outlook profiles were created yesterday.
The office network & internet connection appear to be barely being used.
It really does seem like the Directory lookups are extremely unresponsive.
Antivirus software varies between ESET NOD32 v4, and Microsoft Security Essentials on another computer. Same issues.
I don't think the customer is going to be happy about this at all.
Their Pentium-II 266Mhz, 128mb RAM Windows NT 4 + Exchange 5.5 server was lightning fast compared to this :-(
I will turn on caching of shared folders, now that the data is all uploaded, but that doesn't address the underlying problem of hanging when trying to access the directory/gal server.