Announcing the Send API

Updates

The ImprovMX Send API is now live. Use it to send an email from your domain with one POST request.

How it works

There's no SMTP client to configure and no credentials to manage per alias. Sending an email is a single POST request, authenticated with your ImprovMX API key: 

curl -X POST https://api.improvmx.com/v4/domains/piedpiper.com/emails/outbound \
  -u "api:$API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "from": "richard",
    "to": "[email protected]",
    "subject": "Your Pied Piper password reset",
    "text": "Click the link below to reset your password."
  }'

Use case: Transactional Emails

Use the Send API to send transactional mail such as:

  • Password Resets
  • Magic Links
  • Digital Receipts
  • Alerts

Important: Marketing emails such as newsletters, promotions and drip campaigns are not permitted. If you're not sure which category your mail falls under, read transactional vs. marketing.

Use case: Internet for AI agents

A customer of ours is building a network of agents that talk to each other via email. Previously, this meant setting up and managing an SMTP client on each agent.

The Send API allows the agents to communicate with each other by sending email via a single HTTPS request.

API or SMTP?

Both the API and SMTP sends go through the same infrastructure. As a rule of thumb, use SMTP if you're sending emails through your mail client, and use the Send API if you're sending emails programmatically, through your app.

Below is an in-depth comparison:

Send API SMTP
Best for Your app or a script Your mail client
Setup Your existing API key A credential per alias
Protocol One HTTPS request Connection, handshake, session
Sending from Any alias on the domain The alias the credential is for

Plans and limits

Sending is a paid plan feature. API and SMTP sends share one monthly quota:

Plan Sends / month
Light 750
Premium 12,000
Pro 60,000
Enterprise Unlimited

We recently doubled our sending limits, giving you enough room to try out the Send API.

Getting started

To start, your domain needs to have its DNS configured for sending — the same SPF and DKIM records SMTP uses. After that, create an API key to authenticate your requests. The full reference is in the v4 API docs.

Have any feedback? Tell us at

Thanks,
Matthew Tse
Owner and CEO @ ImprovMX

Matthew Tse

Matthew Tse

Owner and CEO of ImprovMX