# Aggregating and deduplicating AWS managed notifications in User Notifications
<a name="managed-notification-aggregation"></a>

You can aggregate AWS Health managed notifications across accounts within the same organization. To use aggregation, your management account or delegated administrator must [enable trusted access](uno-orgs.md) with AWS Organizations. User Notifications then combines related events from multiple member accounts into a single notification, reducing the total number of notifications you receive.

 For AWS Health managed notifications, User Notifications also deduplicates emails when you share an account contact between the management account (or delegated administrator) and a member account. This reduces the number of individual notifications you receive. 

## Event aggregation process
<a name="aggregation-process"></a>

 AWS managed notifications use an event aggregation logic that combines related events to reduce the number of notifications while maintaining timely delivery of critical information. Events are aggregated based on two key factors: 

**Topics**
+  Communication ID - Events sharing the same `communicationId` are considered related 
**Note**  
Events are sent to User Notifications through an API integration that uses the same format as Amazon EventBridge. For more information, see [Reference: AWS Health events Amazon EventBridge schema](https://docs.aws.amazon.com/health/latest/ug/aws-health-events-eventbridge-schema.html) in the *AWS Health User Guide*.
+  Time window - Events with the same `communicationId` are aggregated within specific time periods based on managed notification sub-category. The following table lists the sub-categories and time windows that apply to AWS Health managed notifications. 


**AWS Health managed notification sub-categories and aggregation time windows**  

<table>
<thead>
  <tr><th><code>Sub-category</code></th><th>Time window</th></tr>
</thead>
<tbody>
  <tr><td><code>Account-Specific Issues</code></td><td>1 minute</td></tr>
  <tr><td><code>Security</code></td><td>10 minutes</td></tr>
  <tr><td><code>Health Operations</code></td><td>10 minutes</td></tr>
  <tr><td><code>Billing Notification</code></td><td>10 minutes</td></tr>
</tbody>
</table>


## Aggregating AWS managed notifications
<a name="notification-aggregation"></a>

User Notifications aggregates event information across accounts as follows:
+ **The same event occurs across multiple accounts within the same organization** – The management account and delegated administrators receive a single aggregate notification containing information about all affected accounts. Each impacted member account receives an individual notification specific to their account.

**Note**  
Aggregation behavior is identical for both the management account and delegated administrator account.

## Deduplicating AWS managed notifications
<a name="managed-notification-dedupe"></a>

User Notifications deduplicates event information across account contacts as follows:
+ **An account contact (root user email or alternate contact email) is shared between the management account or delegated administrator and a member account** – User Notifications sends the aggregate notification about all accounts to the management account or delegated administrator. Individual email notifications to the shared email addresses in member accounts are suppressed.
+ **An account contact (root user email or alternate contact email) is shared between member accounts, but not the management account or the delegated administrator** – Individual notifications are sent per account for each account contact as default notifications. 
+ **Plus address handling** – Plus addressing is a method used to create unique, receive-only email addresses based on an existing email address. You can use plus addressing by adding a plus sign (\+) and any word at the end of your email address. For example, email@example.com and email\+devops@example.com. User Notifications treats email addresses with plus addressing as the same email address. This prevents the same email from being sent to the same inbox multiple times.

Deduplication only applies to account contact emails. AWS managed notifications sent to other member account delivery channels (for example, the Notification Center) are always sent.

**Note**  
User Notifications won't deduplicate events across shared account contacts within the same account. For example, email@example.com and email\+devops@example.com. We recommend you unsubscribe identical account contacts. For more information, see [Adding and removing account contacts for AWS managed notifications in AWS User Notifications](Add-remove-account-contacts.md).