Two numbers control how much you can send through SES. Hitting either does not hurt your reputation, but it can quietly drop mail you thought was on its way.
The two limits
- Sending quota. The maximum number of messages you can send in any rolling 24-hour period.
- Maximum send rate. The maximum number of messages per second.
Both are set per AWS region, so an account that is approved in one region has to be raised separately in another. Quotas are based on recipients, so a message with 10 recipients counts as 10. The quota is calculated over a rolling 24 hours.
How they change
New accounts out of the sandbox start with limits set by AWS. You can ask for more from the console when a launch or a seasonal peak needs it, and a record with a low bounce rate and complaint rate helps your case. The send rate can be exceeded for short bursts, but not for sustained periods.
Why it is worth watching
A rolling 24-hour window means a big batch at noon can block anything you send that evening. Two problems follow:
- You hit the quota during a legitimate peak and the rest of the mail is refused.
- You hit the quota because something went wrong: leaked credentials, a loop in your code, or a bug that resends the same message.
The second case is why a spike in volume is a warning sign as well as a capacity problem. Combined with a high bounce rate, it is how accounts end up under review.
Handling it in your application
Queue outgoing mail and send it at a steady pace below the maximum rate. Retry on throttling errors with a delay. Spread large mailings out instead of sending them all at once. This is also how you warm a new IP without trouble.
Common questions
What happens when I hit the daily quota?
SES rejects further send requests until your rolling 24-hour count drops below the quota. Mail you wanted to go out is delayed or lost unless your application queues and retries.
How do I raise my limits?
You can request an increase from the SES console and explain why you need it. A clean record, with low bounce and complaint rates, makes a request easier to justify.