Reference
Per-second and daily rate limits
Sending limits change from an hourly quota to a per-second rate and a daily limit, shared by the API and SMTP. The default rate is 2 emails per second.
Updated Oct 10, 2025
ChangedLimits & retentionEmail APISMTP relay
Requests over the limit are rejected instead of queued, so configure your client to send at most 2 emails per second or to retry rejected sends. The change was rolled out to workspaces gradually.
See Rate limits.