Hi Fun,
Thank you for your reply. I managed to get it to work by selecting the following Entities: Phone Call, Note and Task in the Workflow.
Now when a Phone Call, Task or Note is added to a Lead and the person adding it isn't the same as the Owner/Assigned user, then an email is sent to the Owner/Assigned person stating a Phone Call, Task or Note has been added.
The mistake I made was choosing the wrong Entity for what I needed.
