If you are seeing the inetinfo.exe process consistently taking up a lot of the Exchange Server's CPU, it is likely because you have enabled "Intelligent Message Filtering" and set it to "archive" spam messages.
What happens is IMF stores these messages in the %programfiles%\exchsrvr\badmail\vsi 1\UCEArchive folder, and over time this folder becomes highly fragmented. The more fragmented this folder becomes, the longer it takes for the disk to respond to SMTP, which in turn causes inetinfo.exe to eat a lot of CPU cycles. The end result is that your Exchange Server starts performing very badly.
Another thing you can do to prove this is the issue is run the Exchange Troubleshooting Assistant. Let it gather data for at least 20 minutes, and the reports that it produces will likely report disk performance problems that it will classify as a bottleneck.
Fixing this is pretty simple, but does take some time...
First off, open your IMF settings and change the "When blocking messages" value to "No Action," "Delete" or "Reject." You will find these options with Exchange System Manager --> Global Settings, and then choose the Properties for Message Delivery.
The you will need to delete all of the files in the UCEArchive folder. You will not be able to open this folder in Windows Explorer because of the size and fragmentation of the folder, so you will need to access it from the command prompt. Open a command prompt and switch to the %programfiles\exchsrvr\badmail\vsi 1\UCEArchive folder (If you want to be amazed at the sheer number of messages, go ahead and execute a directory command...). Once in the directory, type del *.* to remove all of the spam messages in the folder. Please realize this will likely take several hours to complete.