Aria Operations emails delivery are repeating even though the configurations of Aria Operations are not defined to repeat the emails.
Emails will arrive related to old alerts that are maybe already canceled and deleted.
Users will receive the first email immediately, then after some minutes or days the same email will arrive notifying about an old alert.
Following KBs are not the same issue:
Aria Operations 8.18.5
This can happen if the notification settings are defined to use emails that are invalid addresses.
For instance: an user that is no longer in a distribution list or an user directly defined on the notifications that is not valid address.
Issue is not triggered by Aria Operations, the repeated delivers happen at the SMTP level.
Make sure the emails addresses defined on the notifications in Aria Operations are valid and all the emails inside of any distribution list used in the notifications are valid.