Outlook 2013 constantly utilizes on cpu core
Solution 1:
Now in 2020 and using Outlook 365 I had the very same problem: high CPU utilization from Outlook (according to Process Explorer about 12% of the CPU time was used by Outlook). My laptop’s fan was permanently on even if no other program was running.
What helped in my case (after quite some time struggling with this) was to remove the local cache *.ost file in between two Outlook sessions. CPU usage now is typically less than 1%.