# Glossary

The words this documentation uses, defined once.

- **Transactional email**: One email caused by one thing one person did: a receipt, a password reset, a verification code. As opposed to bulk email, which is one message sent to a list.
- **DKIM**: A signature over the message, published as a DNS record, that lets the receiving server prove the mail came from your domain and was not altered. Three CNAME records here, one per key.
- **SPF**: A DNS record listing who may send mail for your domain. A domain may have exactly one; adding a second breaks both.
- **DMARC**: A DNS record telling receivers what to do when DKIM and SPF disagree, and where to send reports about it. Start at p=none and tighten once the reports are clean.
- **MX record**: Where mail for a domain should be delivered. You only need one if you want to receive.
- **Bounce**: The receiving server refused the message. Permanent means the address does not exist; transient means try later, which we do for you.
- **Complaint**: A recipient pressed the spam button, reported back to us through a feedback loop. The address is suppressed.
- **Suppression list**: Addresses on this workspace that hard bounced or complained. Sends to them are refused rather than attempted, which is what protects your sending reputation.
- **Idempotency key**: Your own id for a send. A repeat within 24 hours returns the first result instead of sending again.
- **Warm-up**: Raising volume on a new domain gradually, over days, rather than all at once. Receivers treat a domain with no history and sudden volume as a spammer, because usually it is one.
- **Workspace**: The account boundary. Domains, keys, webhooks, suppression, and quotas all belong to one.
- **llms.txt**: A plain-text file at the root of a site describing it for an AI assistant to read directly. Ours is the whole API in one fetch: https://emails.sh/llms.txt.

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Base URL: https://emails.sh/v1. Auth: `Authorization: Bearer esh_...`.
Whole API in one file: https://emails.sh/llms.txt. All documentation: https://emails.sh/docs.md.