Send email in Go via HTTP API (send and receive)

Send email from Go with one HTTP call — no SMTP, no net/smtp wiring. The send code with net/http, how to receive the reply, and error handling. Free to start.

Sending email from Go usually means net/smtp and a mail server to point it at. A free HTTP email API replaces that with a single net/http call — and it can read the reply, which net/smtp cannot.

Send email in Go

Create a mailbox once, then POST to its send endpoint. A small helper keeps it tidy and surfaces errors:

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
)

const base = "https://login.ollastack.com"
const token = "fmd_…"

func post(path string, body any) ([]byte, error) {
	b, _ := json.Marshal(body)
	req, _ := http.NewRequest("POST", base+path, bytes.NewReader(b))
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()
	data, _ := io.ReadAll(res.Body)
	if res.StatusCode >= 400 {
		return nil, fmt.Errorf("request failed: %s — %s", res.Status, data)
	}
	return data, nil
}

func main() {
	// create a mailbox once
	raw, _ := post("/api/mailboxes", map[string]string{
		"name": "go", "mode": "agent", "handle": "go",
	})
	var mbx struct{ ID string `json:"id"` }
	json.Unmarshal(raw, &mbx)

	// send
	post("/api/mailboxes/"+mbx.ID+"/send", map[string]string{
		"to": "user@example.com", "subject": "Hi", "text": "Sent from Go.",
	})
}

No SMTP host, no port 587, no net/smtp dance — one HTTPS request that returns a msg_… id.

Receive the reply

The same token long-polls for the next inbound message. wait blocks until mail arrives or times out:

res, _ := http.NewRequest("GET",
	base+"/api/mailboxes/"+mbx.ID+"/wait?timeout=60", nil)
res.Header.Set("Authorization", "Bearer "+token)
out, _ := http.DefaultClient.Do(res)
defer out.Body.Close()

var msg struct {
	Subject string   `json:"subject"`
	Codes   []string `json:"codes"`
}
json.NewDecoder(out.Body).Decode(&msg)
fmt.Println(msg.Subject, msg.Codes) // OTP already extracted

That’s the half net/smtp can’t do — read inbound mail and pull the code without parsing MIME.

Why an HTTP API beats net/smtp

net/smtp owns the transport: a server, a port, auth, and connection errors. The API is one request that returns a structured body — a msg_… id on success, a code/message on failure — so you log a real reason. And it receives, which SMTP never did.

Error handling

Always check the status (the helper above does): on 429 back off and retry; on 4xx/5xx read the JSON error body rather than assuming success.

See the email API overview, the Rust version, and the Node.js version.

Get a free token — send and receive from Go, no card.

Last updated June 21, 2026. Spotted something out of date? Email hello@ollastack.com.