>>>Hi,
>>>
>>>I have noticed that the CPU usage of my PC (Windows 7 Pro with 16 GB ram) goes up whenever I start replying to an email. And the longer I reply (or stay in the Reply mode) the higher the CPU until the entire Outlook stops responding. And then I have to close Outlook. As soon as I close it, the CPU goes down.
>>>
>>>What could be causing CPU to go up when replying?
>>>
>>>UPDATE. Another thing I noticed in Task Manager. When I open Outlook, it's memory is no more than 80K. As soon as I click on Reply (to any message), the CPU jumps up from 0 to 20 or 25 right away. The Memory starts growing very fast. I had to cancel Reply when the memory was 196K. So far, Googling for this specific issue didn't produce a solution.
>>
>>Is there any difference if you disable real-time antivirus and anti-spam?
>
>When I disable AV (Avast) and reply to an email, the CPU immediately jumps to 25% and goes up a little (to about 33%) when I start typing. But the memory use goes up all the time as I have the Reply window open. So somewhat of a good news is that I can "control" the CPU with AV but I don't understand why the memory keeps going up.
>Of course, I know why, MS Outlook 365 sucks :) but it does not help me since this is the only tool I have.

If you're talking about Outlook installed on your local PC, my understanding is at this time it's Outlook 2013 (although it might be branded Outlook 365). So you could Google for your problem and that product.

If your CPU goes to 25% and you have a 4 core CPU then probably one core is pinned. Take a look in Task Manager to see which process is using the CPU.

A side note for lurkers: some AV products have problems with Win7/Server 2008 R2:

https://support.microsoft.com/en-us/kb/2028827
https://support.microsoft.com/en-us/kb/2493361