Sandbox mode is automatically activated when you use a test API key (environment: "test"). No code changes or flags are needed — just use your test key.

How it works:

• Emails are fully validated (from, to, subject, template rendering, suppression checks)
• A synthetic message ID is generated (sandbox-{timestamp}-{random})
• The email is logged to your Email Logs with status "sandbox" and an amber badge
• No email is sent via AWS SES — your SES quota and reputation are unaffected
• HTML preview is available in the dashboard just like real emails

This applies to both the HTTP API (POST /v1/send) and SMTP submission relay. Scheduled emails created with a test key will also be sandboxed when they fire.

Use sandbox mode to:

• Validate your email templates and variables during development
• Test API integration without burning SES quota
• Demo the platform without sending real emails
• Run automated tests against the API