setting-up-cloudwatch-alarm-notifications

Create an SNS topic, subscribe the email address with the email protocol, and add the topic ARN to the alarm's AlarmActions. The recipient must confirm the subscription via the confirmation email before notifications are delivered.

Subscribe a phone number to the SNS topic using the sms protocol with the number in E.164 format such as +12345678901. Verify that SMS delivery is supported in your AWS region, as some regions restrict SMS.

The most common cause is an unconfirmed subscription. Run aws sns list-subscriptions-by-topic and check that the subscription status is Confirmed rather than PendingConfirmation, then ask the recipient to confirm via email.

Verify the alarm has the correct SNS topic ARN in its AlarmActions and that ActionsEnabled is set to true using aws cloudwatch describe-alarms. Also confirm the SNS topic policy allows the CloudWatch service principal to publish.

Yes, the setup enables encryption at rest using the AWS managed key alias/aws/sns via set-topic-attributes. A custom KMS key can be specified instead, but the topic policy must still permit CloudWatch to publish.