This is not for intentionally spamming users e.g: Cold emailing users who did not subscribe to your app. This is to avoid unintentionally flooding your users with email who have subscribed to your app. e.g: I ran my cron job 2 times because of a bug and it sent 2 emails for each user.

Another example is retargeting email which are sent for every user visit. If a user visits multiple times on a day, you don't want to send more than 1 email on a single day. This API helps with that.

Then call it flooding, not spamming. Or “rate limiting”.

Ah! Yes! That's much more accurate. I couldn't edit the post, but edited the API description. Thanks for the feedback!