---
updatedAt: 2026-10-13T07:44:14.000Z
agentTools:
  siteIndex: https://developer.rmlconnect.net/llms.txt
  projectIndex: https://developer.rmlconnect.net/route-mobile-project/llms.txt
---

# Appendix

## Glossary of Terms

Use this glossary to understand common SendClean email, authentication, delivery, and API terms.

### Email protocols

| Term     | Definition                                                                                |
| -------- | ----------------------------------------------------------------------------------------- |
| **SMTP** | Simple Mail Transfer Protocol — the protocol used for sending emails across the internet. |

### Authentication and security

| Term          | Definition                                                                                          |
| ------------- | --------------------------------------------------------------------------------------------------- |
| **DKIM**      | DomainKeys Identified Mail — an email authentication method that uses cryptographic signatures.     |
| **SPF**       | Sender Policy Framework — an email authentication method that specifies authorized sending servers. |
| **DMARC**     | Domain-based Message Authentication, Reporting & Conformance — an email authentication policy.      |
| **API Token** | A secure credential used for authentication instead of a password.                                  |

### Delivery and events

| Term                 | Definition                                                                                           |
| -------------------- | ---------------------------------------------------------------------------------------------------- |
| **Webhook**          | An HTTP callback that sends real-time event notifications to your application.                       |
| **Bounce**           | Failed email delivery. Hard bounces are permanent failures, and soft bounces are temporary failures. |
| **Suppression List** | A list of email addresses that should not receive emails from your account.                          |

### API concepts

| Term              | Definition                                                                      |
| ----------------- | ------------------------------------------------------------------------------- |
| **Rate Limiting** | Restrictions on the number of requests allowed in a specific time period.       |
| **Base64**        | An encoding scheme used to represent binary data, such as attachments, as text. |