Why did I get an email from AWS stating that my Amazon SNS subscription was manually deactivated?
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I want to troubleshoot why I received an email from AWS saying that one of my Amazon Simple Notification Service (Amazon SNS) email subscriptions was manually deactivated.
Short description
When messages are published to an SNS topic at a higher rate than the Delivery rate for email messages quota, Amazon SNS deactivates the subscription. When deactivated, the subscription is in a "PendingConfirmation" state.
Amazon SNS automatically deactivates subscriptions when transaction per second (TPS) quotas are breached for several reasons:
Prevent spamming the destination inbox with events.
Protect the recipient mail server from being flooded with messages.
Avoid Internet Service Providers (ISPs) identifying elevated traffic as spam and blocking messages from delivery.
Note: Amazon SNS supports an email message delivery rate of 10 TPS to SNS topics for each AWS account. For more information, see Amazon SNS endpoints and quotas.
Resolution
It's a best practice to avoid subscribing email addresses to high-volume SNS topics. Common use cases for SNS topic email subscriptions include monitoring Amazon CloudWatch alarms and sending usage reports to multiple email addresses.