Send transactional and bulk emails via Mailtrap API or SMTP

This skill covers sending live email through Mailtrap's Email API (REST) or SMTP, across two distinct streams - Transactional (non-promotional, app-generated: password resets, receipts, alerts) and Bulk (promotional/marketing volume) - plus Batch, which is not a third stream but a way to submit up to 500 different messages in one request on whichever stream matches the content. Campaigns is a separate product path entirely, for promotional mail sent to recipients stored as Mailtrap contacts with built-in audience management, scheduling, and reporting.

Use it when integrating, configuring, or troubleshooting live sending via Email API, SMTP, transactional or bulk streams, or batch requests. It explicitly is not the right skill for sandbox-only testing (that's mailtrap-testing-with-sandbox), step-by-step Campaigns UI setup, webhook configuration, or deliverability deep-dives, and it defers to Mailtrap's own docs for exhaustive schemas once the integration path is clear. Integration method follows a strict preference order: a platform-specific plugin or no-code integration first, then an official SDK (Node.js, Python, PHP, Ruby, Java, .NET, CLI), then the raw HTTP Email API, and SMTP only as a last resort for legacy stacks that can't speak HTTP.

Transactional sends go to POST https://send.api.mailtrap.io/api/send (batch: /api/batch); Bulk sends use the identical JSON shape but a different host, POST https://bulk.api.mailtrap.io/api/send - the same $MAILTRAP_API_TOKEN works on both hosts as long as its scope covers that stream. SMTP mirrors this split: live.smtp.mailtrap.io for transactional, bulk.smtp.mailtrap.io for bulk, both on port 587 (or 25/2525/465-SSL) with username api and the API token as password. A typical JSON body has from, to, subject, and text/html, or template_uuid/template_variables to use a Mailtrap-hosted template instead of raw content. The sending API is rate-limited to 150 requests per 10 seconds per token, requiring backoff on 429. Mailtrap automatically manages suppressions - hard bounces, spam reports, unsubscribes - and will not resend to those addresses.

curl -X POST https://bulk.api.mailtrap.io/api/send \
  -H "Authorization: Bearer $MAILTRAP_API_TOKEN" \
  -d '{"from":{"email":"hello@yourdomain.com"},"to":[{"email":"user@example.com"}],"subject":"Promotional","html":"<p>Hi</p>"}'

Official SDKs exist for Node.js, Python, PHP, Ruby, Java, .NET, and a CLI - the skill insists on reading each SDK's README before generating code rather than guessing method signatures from memory. It pairs with mailtrap-setting-up-sending-domain (domain verification required before sends flow) and mailtrap-testing-with-sandbox for safe pre-production testing.

Developers integrating live email sending into an application who need to pick the right stream (transactional vs. bulk), the right transport (API vs. SMTP), and avoid the most common mistake the skill names explicitly: confusing batch (many messages, one request) with bulk (the promotional stream and host) and sending promotional traffic to the transactional host by accident.