Hi, in the original version of the Platform, UserActivityEvent (UAE) stored action-related and email-related user activities. We later broke out email-related activities into the various push_x_emails tables (x = sent | viewed | clicked etc). This was done to improve the performance of the list cutter for large movements.
When an email is clicked, it must have been opened, so an open event is tracked if it doesn't already exist. Email sent activities are only created during blasting.
None of the email-related events are saved to the UAE table. Those methods persist on the UAE model however. Moving this to Push for instance could be a good idea. Please send your suggestions and we'll incorporate them into the work.
Thanks,
John