Definition
Rate limiting restricts the number of API requests that can be sent to an email platform within a specific time period (e.g., 100 requests per minute or 10,000 per hour). When the limit is exceeded, the API returns a 429 Too Many Requests status.
Common Rate Limits
- Sending APIs: Typically limited by emails per second (e.g., 100/sec for Mailchimp, 20/sec for SendGrid free tier)
- Reporting APIs: Higher limits since they do not involve sending
- Management APIs: Usually the most generous limits since they affect only account configuration
Handling Rate Limits
- Implement exponential backoff with retry logic
- Queue requests and send them at a controlled pace
- Monitor usage headers returned by the API to stay within limits
- Request limit increases from your ESP if needed
Why It Matters
Hitting API rate limits can interrupt campaign sends, delay reporting, and break integrations. Proper rate limit handling is essential for reliable email automation at scale.
Related Glossary Terms
BIMI
BIMI (Brand Indicators for Message Identification) is an email standard that allows brands to display their logo next to their emails in supported email clients. It requires DMARC enforcement at quarantine or reject policy.
Customer Data Platform (CDP) for Email
A customer data platform (CDP) is a system that unifies customer data from multiple sources into a single profile, enabling advanced email personalisation, segmentation, and cross-channel coordination.
Email Deliverability
Email deliverability is the ability to land in the recipient's inbox rather than the spam folder. It depends on sender reputation, authentication, list quality, and content practices.
Email Alias
Alternative email addresses or subaddressing patterns that forward to a primary mailbox, affecting subscriber identity tracking and deduplication in email marketing.
Email API Key Management
Email API key management covers creating, storing, rotating, and revoking API credentials used to connect email platforms, ensuring security while maintaining reliable integration access.
Email API Rate Limits
Email API rate limits control the volume and frequency of requests to an ESP's API endpoints, protecting infrastructure from abuse and ensuring fair resource allocation across all customers.