Back in the summer (remember that?) I wrote an article about viewing the Outlook performance counters and how to get them to be visible on Windows 7 and Vista.

I have recently noticed that there are further complications to this.  On one customer site we could not get the Outlook performance counters to register, even after following the guidance in my previous post.

After some research today (huge thanks to Laurent Chaumien in support for finally resolving this!) it turns out that the performance counters are only visible if you are running the same version of perfmon (64-bit or 32-bit) as the version of Outlook (64-bit or 32-bit).

Lets take some examples…

Outlook 32-bit on Windows 32-bit – running Outlook as Administrator should enable the counters and make them visible.

Outlook 32-bit on Windows 64-bit – the default perfmon.exe here will be 64-bit and so will not be able to view the 32-bit performance counters registered by Outlook.  To view these counters you need to run the 32-bit version of perfmon here : C:\Windows\SysWOW64\perfmon.exe

Outlook 64-bit on Windows 64-bit – both Outlook and perfmon are 64-bit and so once you run Outlook as Administrator the perfmon counters should be available.

Note:  You must still run Outlook as an Administrator to enable the counters, in addition to using the correct instance of perfmon!

Hopefully that should work for everyone!