Looks like only trigger action mails displayed in Action log widget.
Steps to reproduce:
1) Create autoregistration action with operations:
Add host
Send message to users
2) Add mail to user profile.
3) Create Dashboard with widget - Actino log.
4) Turn on server and agent.
5) Wait till host added
6) Check Reports->Action log page.

7) Now navigate to Dashboard with Action log.

Result:

Action log widget is empty.

Expected:
I thought that ALL that was displayed on the Action log page should be displayed in the Action log widget.
Documentation/manual doesn't help either.