Send Mail From Your Code.
Or Your Spreadsheet.
One Ecosystem. Two Powerful Products.
Send transactional email from your code with Mailer123, or send personalized email straight from a spreadsheet with Addon Dashboard.
Email API
Mailer123
A developer-first email API — call POST /v1/emails with a scoped Bearer API key to send transactional email from your own product, similar to sending mail through Resend.
- Scoped API Keys
- SPF · DKIM · DMARC
- {{name|fallback}} Tags
- HMAC-Signed Webhooks
- Gmail Sending
- MCP for AI Agents
{
"from": "you@yourapp.com",
"to": "jane@acme.com",
"subject": "Welcome to Acme",
"html": "Hi {{name|there}}…"
}
Google Sheets Extension
Addon Dashboard
Install Addon Dashboard directly in Google Sheets and send personalized emails to every row in your spreadsheet — no code required.
- Google Sheets Add-on
- Mail Merge from Rows
- Merge Tag Personalization
- Scheduled Sends
- Per-Row Tracking
- No-Code Setup
From Integration to Inbox
Three steps, whether you start from code or from a spreadsheet.
- 01
Connect
Create a scoped API key under Settings → API and verify your sending domain.
- 02
Send
Call POST /v1/emails with your key. Merge tags like {{name|there}} resolve at send time.
- 03
Track
Get HMAC-signed webhooks for delivered, opened, clicked, and bounced, or check Analytics.
Everything You Need for Better Email Marketing
Email API
Call POST /v1/emails with a scoped Bearer API key to send transactional email.
- 202POST /v1/emailspriya@sample.co12:04:28
- 202POST /v1/emailsmarcus@demo.io12:04:25
- 202POST /v1/emailsjane@acme.com12:04:22
Domain Verification
Verify SPF, DKIM, DMARC, and BIMI records from the dashboard so mail is trusted.
- SPF
- DKIM
- DMARC
- BIMI
Google Sheets Integration
Send email straight from spreadsheet rows with the Addon Dashboard extension.
Personalization
Merge tags like {{name|there}} resolve at send time, with built-in fallbacks.
Signed Webhooks
HMAC-SHA256 signed events for delivered, opened, clicked, bounced, and more.
Deliverability & Reputation
Monitor inbox placement and sender reputation across every send.
MCP for AI Agents
Connect Claude, ChatGPT, or Cursor to your workspace via the mailer123 MCP server.
Email Logs & Analytics
Search send history and track quota usage across both products.
Two Ways to Send. One Inbox Delivered.
Whether you're a developer or working from a spreadsheet, every email runs through the same trusted sending infrastructure.
Why Choose Us
One platform for every team that sends email — developers in code, everyone else in a spreadsheet.
Simple to Use
A clean API for developers, and a no-code extension for everyone else.
Actionable Insights
See delivery, opens, and clicks for every email you send.
Everything in One Place
Send from your code or your spreadsheet — all on one platform.
Built to Scale
Designed to support growing email sending needs.
Made for Modern Email Marketing
“Placeholder testimonial — We dropped Mailer123's API into our signup flow in under an hour. Transactional email just works now.”
Jordan Ellis
Head of Engineering · Placeholder Co.
“Placeholder testimonial — Addon Dashboard let our sales team send personalized emails straight from a spreadsheet, no engineering time needed.”
Priya Nair
Marketing Lead · Sample Studio
“Placeholder testimonial — Having a real email API and a no-code Sheets option covers every team in our company, not just the developers.”
Marcus Wei
Founder · Demo Labs
Frequently Asked Questions
Everything you need to know about Mailer123 and Addon Dashboard.
Ready to Start Sending Better Email?
Integrate the Mailer123 API in minutes, or install Addon Dashboard in Sheets — and start sending today.