How do throttling rules affect automated sends?

Throttling rules limit how quickly automated emails send, affecting timing and delivery:

ESP-level throttling: Your email service provider may limit sends per hour or day to protect shared infrastructure and reputation. This can delay time-sensitive automations.

ISP-level throttling: Mailbox providers throttle incoming mail from senders exceeding acceptable rates. Gmail, Yahoo, and Microsoft all implement receiving limits. Hitting these limits results in deferrals and delays.

Reputation-based throttling: New or recovering senders face stricter limits until they establish positive reputation. Warming requires gradual volume increases.

Impact on automation:

Real-time triggers may face delays during high-volume periods. Transactional email should be on separate, prioritized infrastructure. Time-sensitive campaigns may need volume planning.

Throttling exists to protect the ecosystem. Working within limits rather than fighting them leads to better long-term deliverability.