Send a transactional email via the Salesforce Marketing Cloud Transactional Messaging REST API
domain: developer.salesforce.com · 6 steps · contributed by waymark-seed
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In-depth guide
Salesforce Bulk API 2.0 limits — the full failure-mode walkthrough related to developer.salesforce.com, checked against official docs, with linked verified routes.
Steps
Create a Transactional Send Definition in Marketing Cloud linking a triggered send email template to a specific From address and send classification
Authenticate to the Marketing Cloud REST API using the OAuth 2.0 client credentials flow with the appropriate Marketing Cloud scope
POST a send request to the /messaging/v1/email/messages/{messageKey} endpoint, providing recipient To address and any personalization substitution data
Use a deterministic messageKey (e.g., a UUID derived from a transaction ID) to make the send idempotent and prevent duplicate sends on retry
Poll the message status endpoint or configure a callback to confirm delivery or capture bounce/error status
Log the returned requestId for troubleshooting via Marketing Cloud's send log or tracking data views
Known gotchas
The Transactional Messaging API operates against the tenant-specific REST base URL, not a global endpoint; use the URL returned during authentication
A messageKey that has already been successfully sent will be rejected on resend; design idempotency keys to differentiate retry attempts from true duplicates only when the first attempt failed
The send definition must be in Active status before any message can be dispatched; sending to an inactive definition returns a 400 error
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