Monitoring AWS SES Bounce Rate with CloudWatch Alarm: Recommended Thresholds

Posted on by user

1. What is the SES Bounce Rate?

In AWS Simple Email Service (SES), the bounce rate represents the percentage of emails that fail to be delivered.

  • Soft Bounce: The recipient’s email server temporarily rejects the email (e.g., inbox is full).
  • Hard Bounce: The email is permanently undeliverable (e.g., the email address does not exist).

A high bounce rate can lead to account restrictions or suspension by AWS SES.

2. Recommended SES Bounce Rate Thresholds

AWS recommends keeping the bounce rate below 2.0%. If the bounce rate exceeds this, SES may impose sending restrictions.

Bounce RateRisk LevelAction to Take
< 0.5%SafeNo action needed
0.5% – 1.5%Slightly highClean up the mailing list
1.5% – 2.0%DangerousRemove hard bounces and verify recipients
> 2.0%Very risky 🚨SES may impose sending limits

3. Setting Up a CloudWatch Alarm for SES Bounce Rate

AWS CloudWatch provides a metric called SES:Reputation.BounceRate, which can be used to monitor the bounce rate.

Recommended CloudWatch Alarm Settings

  • Metric: SES:Reputation.BounceRate
  • Statistic: Average
  • Period: 1 hour
  • Thresholds:
    • Warning Alarm: 1.0% (0.01)
    • Critical Alarm: 2.0% (0.02)
  • Actions: If bounce rate exceeds 2.0%, trigger SNS notification or Lambda function for automated handling.

AWS CLI Command for Creating the CloudWatch Alarm

aws cloudwatch put-metric-alarm \\
  --alarm-name "SES-BounceRate-Alarm" \\
  --metric-name "Reputation.BounceRate" \\
  --namespace "AWS/SES" \\
  --statistic "Average" \\
  --threshold 0.02 \\
  --comparison-operator "GreaterThanOrEqualToThreshold" \\
  --evaluation-periods 1 \\
  --period 3600 \\
  --alarm-actions "arn:aws:sns:your-region:your-account-id:your-topic"

4. What to Do If the Bounce Rate Is Too High

  1. Clean Your Email List
    • Remove email addresses that hard bounced immediately.
    • Remove soft bounces if they occur multiple times.
  2. Set Up Bounce Notifications via SNS
    • Configure AWS SES to send bounce notifications to an SNS topic.
    • Use an AWS Lambda function to process bounce events and update your mailing list.
  3. Optimize Sending Domain Settings
    • Ensure SPF, DKIM, and DMARC records are correctly configured.
    • Check if your sending IP is blacklisted and request removal if necessary.

Conclusion: Best Bounce Rate Thresholds for CloudWatch

  • Warning Alert: 1.0% (0.01)
  • Critical Alert: 2.0% (0.02)