Improvements have been made to Alert functionality with regards to maintenance windows.

If a DOWN alert occurs, and a maintenance window is then created for the check, the corresponding UP alert will be sent when the check recovers, whether the check is still within the maintenance window or not. This ensures that you are notified that the check has returned to UP status regardless of any maintenance window that has been created. 

When there is no maintenance window active, DOWN and UP notifications will continue to function as normal. Escalation contacts will also follow the new functionality.

For more information, please read our documentation on the Alert Improvements.