Glossary
Concise definitions for the concepts that appear across this site.
Transactional email
One-to-one email triggered by user action.
Marketing email
One-to-many email sent on the senders schedule.
SMTP
The protocol that delivers email between mail servers.
API vs SMTP
When to use HTTP API versus SMTP relay.
Idempotency keys
A header that prevents duplicate sends on retry.
Event stream
Per-message lifecycle events (delivered, bounced, opened, clicked).
Suppressions
A list of recipients the provider refuses to send to.
Dedicated IP
A sending IP reserved for one customer.
Shared IP
A sending IP used by many customers of a provider.
IP warming
Gradually ramping volume on a new IP to build reputation.
SPF
A DNS record listing which servers may send for your domain.
DKIM
A cryptographic signature attached to outbound mail.
DMARC
A policy that tells mailbox providers what to do when SPF or DKIM fail.
BIMI
A standard for showing your logo next to authenticated mail.
Sandbox mode
A starter mode that limits sending to verified addresses.