TR;DR

We often use https://www.minuteinbox.com/ to test CIAM solutions with unique email addresses, but is it perfect? With our domain and OpenTrashmail, we can improve our solution. After a year or two, we can still activate the old account (reset password or OTP access) - it is not possible via 10 min mail (the domain for email is changing, and the old one is not accessible).

Setting Up OpenTrashmail with Your Domain for E2E Testing

Email testing is often a critical part of end-to-end (E2E) testing for applications that send notifications, verification codes, or other important communications. Running our disposable email service gives you full control over test mailboxes and simplifies your testing workflow. Here’s how to set up OpenTrashmail:

What is OpenTrashmail?

OpenTrashmail is an open-source disposable email service that we can self-host. It provides temporary email addresses that can be used for testing purposes, allowing us to automatically, via REST JSON API, verify email delivery and content in our test suites, for example, PlayWright test cases, but also with manual verification.

Prerequisites

  • A domain we control (e.g., yourdomain.com).
  • Access to modify our domain’s DNS records.
  • Docker and/or Docker Compose installed on server/workstation.
  • Basic understanding of DNS configuration.
  • Basic understanding of Docker and Docker Compose.

Step 1: Configure DNS Records

First, we need to decide on the name for the email domain and set up the proper DNS records (the hardest part):

  1. Add an MX record for subdomain:

    @ IN MX 10 mail.yourdomain.com.

  2. Add an A record for the mail subdomain pointing to your server’s IP (the server must expose the 25 port for SMTP):

    mail IN A your.server.ip.address

Step 2: Create a Docker Compose File

Create a docker-compose.yml file with the following configuration:

services:
  opentrashmail:
    image: hascheksolutions/opentrashmail:1
    container_name: opentrashmail
    ports:
      - "25:25"
      - "80:80"
    environment:
       - DELETE_OLDER_THAN_DAYS=2
       - DISCARD_UNKNOWN=false
       - DATEFORMAT='D.M.YYYY HH:mm'
       - DOMAINS=mail.yourdomian.com
  tunnel:
     image: cloudflare/cloudflared:latest
     container_name: opentrashmail_tunnel
     environment:
        - TUNNEL_TOKEN=${TUNNEL_TOKEN}
     #restart: unless-stopped
     command: tunnel run

Replace yourdomain.com, TUNNEL_TOKEN with your actual values. I recommend using Cloudflare Tunnel for secure access to the OpenTrashmail service with reverse proxy and SSL. Please remember that you need to open and forward the 25 port on your server.

Step 3: Launch the Container

Run the following command in the directory containing your docker-compose.yml file:

docker-compose up -d

This will download the OpenTrashmail image and start the service in the background.

Step 4: Use OpenTrashmail

Once the container is running, we should be able to access the OpenTrashmail web interface via Cloudflare reverse proxy or on the host with the HTTP 80 port.

Step 5: Integrating with E2E Tests

Now that OpenTrashmail is running, we can use its API to access the temporary mailboxes created for our domain.

Via REST JSON endpoint https://mail-website.yourdomain.com/json/[email protected] we can check the mailbox. There is one disadvantage - the empty mailbox is represented by array response, but with email(s) the structure is like below:

{
  "1740855216429": {
    "email": "[email protected]",
    "id": "1740855216429",
    "from": "\"External ID Factorlabs - Customers (via Microsoft)\" \[email protected]\u003E",
    "subject": "Your External ID Factorlabs - Customers account verification code",
    "md5": "35bfa0213771626280517948da315066",
    "maillen": 11120,
    "body": "To access External ID Factorlabs - Customers's apps and resources, please use the code below for account verification. The code will only work for 30 minutes.\r\n\r\nAccount verification code:\r\n13652349\r\n\r\n\r\n                If you didn't request a code, you can ignore this email.\r\n             \r\nPrivacy Statement: https://go.microsoft.com/fwlink/?LinkId=521839\r\nMicrosoft Corporation, One Microsoft Way, Redmond, WA 98052\r\n",
    "attachments": []
  },
  "1740947742229": {
    "email": "[email protected]",
    "id": "1740947742229",
    "from": "\"External ID Factorlabs - Customers (via Microsoft)\" \[email protected]\u003E",
    "subject": "Your External ID Factorlabs - Customers account verification code",
    "md5": "53f3c02c66171e6aa423e0d159f43a14",
    "maillen": 11123,
    "body": "To access External ID Factorlabs - Customers's apps and resources, please use the code below for account verification. The code will only work for 30 minutes.\r\n\r\nAccount verification code:\r\n19739883\r\n\r\n\r\n                If you didn't request a code, you can ignore this email.\r\n             \r\nPrivacy Statement: https://go.microsoft.com/fwlink/?LinkId=521839\r\nMicrosoft Corporation, One Microsoft Way, Redmond, WA 98052\r\n",
    "attachments": []
  }
}

Summary

Setting up OpenTrashmail with your domain provides a reliable way to test email functionality in your applications without external dependencies. It is easy to host and can be used with any domain owned by us. It doesn’t need to be your official product or company domain (a subdomain is enough).

Do you know any other solutions for temporary mailboxes? Share them via LinkedIn or Bluesky.