Documented steps

Create/store the template on the sending domain first (Mailgun dashboard or templates API); note the template name
POST {region-base}/v3/{domain}/messages with Basic auth ('api' + key), fields: from, to, subject, and 'template' = the stored template name
Pass variables as 't:variables' = a JSON object string, e.g. t:variables='{"name":"Jo","code":"ABC123"}'; the template substitutes {{name}} etc. (Handlebars with Mailgun's helpers: if/unless/each/with/equal)
For raw MIME sends (/messages.mime) pass variables via the X-Mailgun-Template-Variables header instead
HTTP 200 returns queued message id as usual
Docs: https://documentation.mailgun.com/docs/mailgun/user-manual/sending-messages/send-templates

Known gotchas

Template name is case-sensitive and must already exist on that domain — otherwise the send fails (400/404)
Undefined variables render as empty strings, not errors — typos in {{names}} produce silently blank content
t:variables must be valid JSON (as a string form field); malformed JSON → 400
Handlebars partials are not supported; only Mailgun's documented helpers
t:variables counts toward the 16KB combined limit on o:/h:/v:/t: parameters — keep payloads small
The form 'subject' does not override a subject baked into the template version; use a variable in the template subject for dynamic subjects

mailgun.com · 6 steps · unrated

Send an email with a Postmark template (POST /email/withTemplate)

postmarkapp.com · 5 steps · unrated

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Send a Mailgun email using a stored template with variables

Documented steps

Known gotchas

Related routes

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