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For developers

Send email from your app

Send a password reset, launch a campaign, or keep a customer conversation moving. Connect your application to the same email workspace your team uses.

Start free Read the quickstart

Connect with SMTP

Use smtp.sendmailos.com with STARTTLS on port 2525 or implicit TLS on port 2465. Create a sending-only password and use a verified From address. Delivery follows your domain’s SES, connected-server, or hybrid route.

SMTP attachments are not supported yet. See the full SMTP setup

A different way to send

Your server. Your IP.
No per-email platform fee.

Connect your own VPS to SendMailOS. Create campaigns and manage your email in our platform, then send through your own server and IP.

  • Own-server sends do not use hosted email credits
  • Connect one server with Starter at €12/month
  • Keep campaigns, contacts, and reports in one place
See how it works Compare plans

Your plan and VPS costs still apply. Daily warm-up, safety checks, fair-use, and your server’s capacity apply to sending.

Connect your own sending server and IP to SendMailOS, with no platform per-email fee on a paid plan
Product illustration · Example setup

Setup checklist

Send email with the API

Create an API key, verify your sending domain, and make a request to POST /v1/emails. Use the email ID and delivery events to follow what happens next.

Test-mode keys let you simulate development sends without delivering to real mailboxes. Use an idempotency key when retrying the same send request.

Send your first email
SendMailOS developer preview showing an example email API request, 202 response, and delivery event
Product preview · Example data

Email API example

Track delivery with webhooks

Use plain HTTP from your backend. Start with one message, then explore templates, subscribers, broadcasts, workflows, and conversations as your product grows.

A 202 Accepted response means the message was accepted for processing. Check its status or subscribe to a delivery webhook for the result.

Explore authentication and scopes
Send an email · cURL
curl https://api.sendmailos.com/v1/emails \
  -H "Authorization: Bearer sk_live_your_key" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: your-unique-request-id" \
  -d '{
    "from": "hello@yourdomain.com",
    "to": "customer@example.com",
    "subject": "A good place to start",
    "html": "<h1>Welcome aboard.</h1>"
  }'

Replace the example key and addresses with your own verified sending details.

Email tools for developers

Send email with SMTP

Connect an application or WordPress mail plugin with a sending-only SMTP password. Use STARTTLS on port 2525 or implicit TLS on port 2465.

Read the SMTP guide

Receive delivery events

Receive signed delivery, open, click, bounce, and incoming-message events. Verify signatures and make your receiver safe to retry.

Connect a webhook

Manage conversations with the API

Create a thread, send a message, and receive the reply event. Tie a conversation to the booking or order it belongs to.

Review reply-capture setup

Template Studio MCP

Create editable templates with MCP

Connect a compatible remote MCP client to Template Studio. Ask it to create a responsive email or update an existing template in an organization you have approved.

The assistant saves structured rows, columns, and blocks. Your team can keep editing the design in SendMailOS after the conversation ends.

https://dash.sendmailos.com/api/mcp

Read the Template Studio setup guide
SendMailOS email template editor preview with editable content blocks and example templates
Product preview · Example data

Set up your MCP connection

Choose access permissions

The remote MCP connection uses OAuth with PKCE. Sign in to SendMailOS, choose the organizations, and approve the template permissions shown.

Select your organization

Name an approved organization in your prompt. Tools resolve its ID and keep the template in that organization.

Edit templates before publishing

Refine generated content in the visual editor. Template MCP manages editable templates and offers additional read tools when their permissions are approved.

Questions and answers

Frequently asked questions

Do I need a particular SDK?

No. The HTTP API works with standard requests from your backend. The documentation includes request shapes and examples to help you integrate with your stack.

Can I use the same API for marketing and transactional email?

The platform supports both. Use email sends for application messages, and the broadcast and subscriber resources for audience-oriented sending.

Do I paste my API key into an MCP assistant?

No. Template Studio’s remote MCP connection uses OAuth. Your client opens SendMailOS so you can sign in and approve access without sharing an API key or password in chat.

Can Template MCP control every part of my account?

Template MCP creates, edits, renders, and publishes templates in approved organizations. With additional permissions, it can also read subscribers, broadcasts, and email analytics. It does not send campaigns or change workflows.

Start free

Connect your app to SendMailOS

Start with the quickstart. Keep building with the API.

Start free