Rate limiting
Going over 10 requests per second returns429 with the code rate_limited. The response carries Retry-After with the number of seconds to wait. Back off and retry; with an idempotency key, retries are safe.
Sending reputation
PulseSend watches each team’s bounce and complaint rates, the numbers mailbox providers judge senders by. Keep bounces under 4% and complaints under 0.08%. Rates are computed on live emails from the last 30 days whose outcome is known (delivered, bounced or marked as spam), once you have at least 100 of them. Test emails never count. They are checked every time a bounce or complaint comes in. When a rate goes over its limit, sending is paused for the whole team: every send returns403 team_paused, the team owner gets an email and the dashboard shows a banner. Clean up your recipient list, then contact support to reactivate sending. Rates start again from zero after reactivation.
Keep both rates low by sending only to people who asked for your emails and removing addresses that bounce.