I have a severe performance problem with Outlook 2007 on Vista Ultimate where
Outlook consumes 90-100% of the CPU (fortunately I have a Core 2 Duo) and the
process memory, which starts at around 18 MB, keeps climbing endlessly over
time. The highest I have seen before stopping Outlook was over 900 MB of RAM
for the Outlook.exe process.

So here is what I did to get there:

- I got a new Dell XPS M1710 with Vista Home Premium, and no Office
installed. This is one of the most powerful laptops in the world, it should
*not* have any performance problems. Everything else runs with stellar speed.
- I upgraded to Vista Ultimate using my MSDN Premium subscription.
- I installed Office Ultimate 2007, including Outlook.
- I used the *exact* same configuration settings for my company's Exchange
server as I had in Outlook 2007 on my other Windows XP laptop, which did not
have any performance problems other than being a 3+ year old laptop.
- I use cached Exchange mode since I have several computers. Not using
cached mode is not an option.
- I have a fairly large local OST file, about 2.7 GB in size, but it was not
a problem on my other laptop and home compute, and still isn't.
- I have run Windows Update and everything is up-to-date.

The behavior I get:
- I launch Outlook. I have tried this both on my internal company network
when connected to the domain, or from the outside using Exchange over HTTP.
Same behavior.
- The initial Outlook process is about 18 MB in size.
- Outlook is almost non responsive since it automatically starts consuming
90-100% of the CPU core it runs on. If I click something, it takes about 2-4
seconds for anything to happen since there is a short pulse where the CPU
usage dips by about 10% every few seconds.
- I have had instances where Oulook was crashed and it had to check the OST
file for corruption, but even after the check was complete, or if there was
no check because Oulook exited properly, I get the same behavior.
- When I monitor the process using the task manager, I see that the process
memory is slowly climbing. And it does not stop. I have seen it go as high as
over 900 MB in size.
I keep receiving emails normally, but of course, with so little CPU, getting
access to them takes time.
- Outlook is not reporting any messages anywhere like "receiving mails", or
"archiving messages", or anything like that. From a UI point of view, it is
doing nothing.
- I can close Outlook (with the usual 2-4 seconds responsiveness delay), but
the longer I wait, the longer it takes for the process to eventually get
completely unloaded.

Here is what I have observed and tried:
- As I said, all updates in Windows Update have been installed successfully.
- I also installed the Outlook update from April 13 2007 from KB article
933493, which is supposed to address performance problems with large OST/PST
files. it did not fix anything.
- I tried working offline to see if it was a networking issue. No change.
- I disabled indexing on the Exchange mailbox. No change.
- Last night, I severly reduced the number of emails by archiving all of
2006 from my Inbox into a separate PST file. We're talking about 8000 emails
that were removed here. I used my WinXP laptop to do the transfer since
Outlook was just too slow on my new Vista laptop to do the move. Still the
same problem, although I have noticed that my OST file is still big at 2.7 GB.
- I used the SysInternals Process Monitor to check the Outlook.exe process.
What I noticed is there are over 15 instances of mso.dll running, and these
are the ones that seem to receive the CPU cycles the most.
- Using Process Monitor, I checked the file operations being performed since
my Hard drive would pretty much always be in use while Outlook is running.
There were massive "Read" entries on my OST file, and no writes, which means
it's not archiving anything. It seems like it's reading my OST file and
putting (or leaking) something in memory. I have no idea what it's doing.

I am desperate. I need help. My laptop is unbelievably awesome, but without
Oulook, my productivity is crippled and Outlook web Access is just not good
enough for all-day use.

If you need me to run any kind of test or need more information, please let
me know and I'll provide additional details.

Many thanks for your help.

Nick Landry, MVP
Visual Developer - Device Application Development
Principal Architect - Infusion Development, NYC