You are getting SQL attachability notifications about the job being skipped when there will not be any sql server installed on the core nor where there will be an SQL attachability check enabled on any protected sql server agent.
This is the informational alert that is received on the Events tab:
"Nightly attachability job has been skipped. Reason: There are no SQL Server instances configured for attachability check on the Core."
These alerts occur frequently and need to be disabled.
To disable the event notifications/alerts about the SQL attachability jobs being skipped.
On the Core:
1. Navigate to the Configuration tab -> click on Events -> under the Notification Groups
2. Click on the tools icon on the right
3. Navigate to the "Attachability" option under the Enable Events tab
4. Expand the "Nightly" section
5. Uncheck the checkbox for "NightlyAttachabilitlySkipped"