Sending Email

Holamail is a lightweight SMTP listener. It accepts the basic SMTP commands HELO/EHLO, MAIL FROM, RCPT TO, DATA, and QUIT, then logs the message. It does not deliver email to external recipients.

Connection Details

Holamail does not support STARTTLS or SMTP AUTH.

SMTP Protocol Flow

The raw SMTP conversation follows this sequence:

1HELO client.example.com
2MAIL FROM:<noreply@example.com>
3RCPT TO:<user@example.com>
4DATA
5Subject: Hello from Holamail
6
7This message will be logged by Holamail.
8.
9QUIT

Examples

Using curl

curl --url smtp://smtp.testmail.hola.cloud:25 \
     --mail-from noreply@example.com \
     --mail-rcpt user@example.com \
     --upload-file email.txt

GET / HTTP/1.1
Host: smtp.testmail.hola.cloud:25

package main

import (
	"fmt"
	"io"
	"net/http"
)

func main() {
	req, err := http.NewRequest("GET", "smtp://smtp.testmail.hola.cloud:25", nil)
	if err != nil {
		panic(err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	responseBody, err := io.ReadAll(resp.Body)
	if err != nil {
		panic(err)
	}
	fmt.Println(string(responseBody))
}

<?php
$ch = curl_init();

curl_setopt_array($ch, [
    CURLOPT_URL => 'smtp://smtp.testmail.hola.cloud:25',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CUSTOMREQUEST => 'GET',
]);

$response = curl_exec($ch);
if ($response === false) {
    throw new Exception(curl_error($ch));
}
curl_close($ch);

echo $response;

import requests

response = requests.request(
    "GET",
    "smtp://smtp.testmail.hola.cloud:25"
)

print(response.text)

const response = await fetch("smtp://smtp.testmail.hola.cloud:25", {
  method: "GET"
});

console.log(await response.text());

const response = await fetch("smtp://smtp.testmail.hola.cloud:25", {
  method: "GET"
});

const text = await response.text();
console.log(text);

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
    public static void main(String[] args) throws Exception {
        var request = HttpRequest.newBuilder()
            .uri(URI.create("smtp://smtp.testmail.hola.cloud:25"))
            .method("GET", HttpRequest.BodyPublishers.noBody())
            .build();

        var response = HttpClient.newHttpClient().send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body());
    }
}

Where email.txt contains:

1Subject: Hello from Holamail
2
3This message will be logged by Holamail.

Plain TCP Session

1telnet localhost 2525

Then enter:

1HELO client.example.com
2MAIL FROM:<noreply@example.com>
3RCPT TO:<user@example.com>
4DATA
5Subject: Local Holamail test
6
7Hello from a local Holamail listener.
8.
9QUIT

Using Go's net/smtp

 1package main
 2
 3import (
 4    "log"
 5    "net/smtp"
 6)
 7
 8func main() {
 9    to := []string{"user@example.com"}
10    msg := []byte("To: user@example.com\r\n" +
11        "Subject: Hello from Holamail\r\n" +
12        "\r\n" +
13        "This message will be logged by Holamail.\r\n")
14
15    err := smtp.SendMail("smtp.testmail.hola.cloud:25", nil,
16        "noreply@example.com", to, msg)
17    if err != nil {
18        log.Fatal(err)
19    }
20}

Using Python's smtplib

 1import smtplib
 2from email.message import EmailMessage
 3
 4msg = EmailMessage()
 5msg.set_content("This message will be logged by Holamail.")
 6msg["Subject"] = "Hello from Holamail"
 7msg["From"] = "noreply@example.com"
 8msg["To"] = "user@example.com"
 9
10with smtplib.SMTP("smtp.testmail.hola.cloud", 25) as server:
11    server.send_message(msg)

Expected Behavior

Holamail accepts syntactically valid SMTP input and logs the message. It is useful for confirming that an application can speak SMTP without sending real email.

Unsupported features include external delivery, HTTP APIs, STARTTLS, AUTH, rate limiting, templates, analytics, and tracking.