Open Trashmail

Selfhosted trashmail solution - Receive Emails via Web UI, JSON API, RSS feed and Custom Webhooks

Changelog

Features

• Python-powered mail server that works out of the box for any domain you throw at it
• RSS feed for every email address
• JSON API for integrating it in your own projects. Can be used to automate 2fa emails
• Webhooks with per-email configuration and customizable JSON payloads
• Handles attachments
• Supports Plaintext, STARTTLS and TLS on connect
• Web interface
  • Automatic dark/light mode switcher
  • Download attachments
  • Delete emails
  • Generate random email addresses
  • View server logs and list all accounts as admin
• 100% file based, no database needed
• Can be used as Email Honeypot or to programmatically solve 2fa emails
• No need to pre-create email addresses. Any valid email address can be sent to

General API calls and functions

Endpoint	Explanation	Example output
/rss/[email-address]	Renders RSS XML for rss clients to render emails
/api/raw/[email-address]/[id]	Returns the raw email of the address. Warning: Output can be as large as the email itself so might be up to 20mb for mails with large attachments
/api/attachment[email-address]/[attachment-id]	Returns the attachment with the correct mime type as header
/api/delete/[email-address]/[id]	Deletes a specific email message and their attachments
/api/deleteaccount/[email-address]	Deletes all messages and attachments of this email account
/api/webhook/get/[email-address]	Get webhook configuration for an email address
/api/webhook/save/[email-address]	Save webhook configuration for an email address
/api/webhook/delete/[email-address]	Delete webhook configuration for an email address

JSON API

Endpoint	Explanation	Example output
/json/[email-address]	Returns an array of received emails with links to the attachments and the parsed text based body of the email. If ADMIN email is entered, will return all emails of all accounts
/json/[email-address]/[id]	To see all the data of a received email, take the ID from the previous call and poll this to get the raw and HTML body of the email. Can be huge since the body can contain all attachments in base64
/json/listaccounts	If SHOW_ACCOUNT_LIST is set to true in the config.ini, this endpoint will return an array of all email addresses which have received at least one email

Configuration

Just edit the config.ini You can use the following settings

• URL -> The url under which the GUI will be hosted. No tailing slash! example: https://trashmail.mydomain.eu
• DOMAINS -> Comma separated list of domains this mail server will be receiving emails on. It's just so the web interface can generate random addresses
• MAILPORT-> The port the Python-powered SMTP server will listen on. Default: 25
• ADMIN -> An email address (doesn't have to exist, just has to be valid) that will list all emails of all addresses the server has received. Kind of a catch-all
• DATEFORMAT -> How should timestamps be shown on the web interface (moment.js syntax)
• PASSWORD -> If configured, site and API can't be used without providing it via form, POST/GET variable password or http header PWD (eg: curl -H "PWD: 123456" http://localhost:8080/json...)
• ALLOWED_IPS -> Comma separated list of IPv4 or IPv6 CIDR addresses that are allowed to use the web UI or API
• ATTACHMENTS_MAX_SIZE -> Max size for each individual attachment of an email in Bytes
• MAILPORT_TLS -> If set to something higher than 0, this port will be used for TLSC (TLS on Connect). Which means plaintext auth will not be possible. Usually set to 465. Needs TLS_CERTIFICATE and TLS_PRIVATE_KEY to work
• TLS_CERTIFICATE -> Path to the certificate (chain). Can be relative to the /python directory or absolute
• TLS_PRIVATE_KEY -> Path to the private key of the certificate. Can be relative to the /python directory or absolute
• WEBHOOK_URL -> Global webhook URL. If set, will send a POST request to this URL with the JSON data of the email as body for all emails (unless overridden by per-email webhook)
• ADMIN_ENABLED -> Enables the admin menu. Default false
• ADMIN_PASSWORD -> If set, needs this password to access the admin menu

Docker env vars

In Docker you can use the following environment variables:

ENV var	What it does	Example values
URL	The URL of the web interface. Used by the API and RSS feed	http://localhost:8080
DISCARD_UNKNOWN	Tells the Mailserver to wether or not delete emails that are addressed to domains that are not configured	true, false
DOMAINS	The whitelisted Domains the server will listen for. If DISCARD_UNKNOWN is set to false, this will only be used to generate random emails in the webinterface
SHOW_ACCOUNT_LIST	If set to true, all accounts that have previously received emails can be listed via API or webinterface	true,false
ADMIN	If set to a valid email address and this address is entered in the API or webinterface, will show all emails of all accounts. Kind-of catch-all	test@test.com
DATEFORMAT	Will format the received date in the web interface based on moment.js syntax	"MMMM Do YYYY, h:mm:ss a"
SKIP_FILEPERMISSIONS	If set to true, won't fix file permissions for the code data folder in the container. Useful for local dev. Default false	true,false
PASSWORD	If configured, site and API can't be used without providing it via form, POST/GET variable password or http header PWD	yousrstrongpassword
ALLOWED_IPS	Comma separated list of IPv4 or IPv6 CIDR addresses that are allowed to use the web UI or API	192.168.5.0/24,2a02:ab:cd:ef::/60,172.16.0.0/16
ATTACHMENTS_MAX_SIZE	Max size for each individual attachment of an email in Bytes	2000000 = 2MB
MAILPORT_TLS	If set to something higher than 0, this port will be used for TLSC (TLS on Connect). Which means plaintext auth will not be possible. Usually set to 465. Needs TLS_CERTIFICATE and TLS_PRIVATE_KEY to work	465
TLS_CERTIFICATE	Path to the certificate (chain). Can be relative to the /python directory or absolute	/certs/cert.pem or cert.pem if it's inside the python directory
TLS_PRIVATE_KEY	Path to the private key of the certificate. Can be relative to the /python directory or absolute	/certs/privkey.pem or key.pem if it's inside the python directory
WEBHOOK_URL	If set, will send a POST request to this URL with the JSON data of the email as body. Can be used to integrate OpenTrashmail in your own projects	https://example.com/webhook
ADMIN_ENABLED	Enables the admin menu. Default false	false / true
ADMIN_PASSWORD	If set, needs this password to access the admin menu	123456

TLS

Since v1.3.0 TLS and STARTTLS are supported by OpenTrashmail.

What you should know

Be aware there are two ways to use TLS with email

1. STARTTLS
2. TLS on Connect (TLSC)

STARTTLS does not require a specific port as it starts out as plaintext and then upgrades to TLS if the server advertises the "STARTTLS" command (which OpenTrashmail does automatically if the Certificate and key settings are configured). Since it's run on the default MAILPORT you don't need to open other ports for it to work.

TLS on connect is wrapping TLS around the exposed ports so it's not possible to talk to it in plaintext and therefore it needs a different port to work. Usually port 465 is used for this.

About the certificates

For TLS to work you first need a certificate that corresponds with the hostname of the SMTP server. This can be done using Lets'encrypt and even works with wildcard certificates.

For testing environments you can create a certificate by running the following command from inside the python folder:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem   -days 365 -nodes -subj '/CN=localhost'

You then need to set the settings for MAILPORT_TLS (not needed if you only want to support STARTTLS), TLS_CERTIFICATE and TLS_PRIVATE_KEY.

Testing TLS

The /docs/Dev.md file contains a few hints on how to debug and test TLS and TLSC connections. It uses the tool swaks which should be avaialable in every package manager.

Roadmap

• Mail server
  • Storing received mails in JSON
  • Storing file attachments
• Docker files and configs
• Web interface
  • Choose email
  • Get random email address
  • Download attachments safely
  • Display Text/HTML
  • API so all features from the site can also be automated and integrated
  • Automatically check for new emails while on site
  • Admin overview for all available email addresses
  • Option to show raw email
  • Delete messages
  • Make better theme
  • Secure HTML, so no malicious things can be loaded
  • Display embedded images inline using Content-ID
• Configurable settings
  • Choose domains for random generation
  • Choose if out-of-scope emails are discarded
  • Automated cleanup of old mails
  • Optionally secure whole site with a password
  • Optionally allow site to be seen only from specific IP Range
  • Honeypot mode where all emails are also saved for a catchall account (implemented with the ADMIN setting)

Quick start

Set the MX Records

In your DNS panel create a MX record for your domain pointing to the IP of the server hosting OpenTrashmail.

The following example will allow you to send emails to example.com

mail.example.com.	IN	A		93.184.216.34
example.com.    14400   IN      MX      10      mail.example.com.

This advanced example will allow you to use a wildcard domain:

mail.example.com.	IN	A		93.184.216.34
*.example.com.    14400   IN      MX      10      mail.example.com.

This in combination with the configuration option "DOMAINS" (eg docker parameter -e DOMAINS="*.example.com") will allow you to use any address with any subdomain of example.com (eg test@robot.example.com, john@lynn.example.com, etc..)

Running in docker (preferred)

Simple start with no persistence

docker run -it -p 25:25 -p 80:80 -e URL="https://localhost:80" hascheksolutions/opentrashmail:1

Saving data directory on host machine

docker run -p 80:80 -p 25:25 -e URL="https://localhost:80" -v /path/on/host/where/to/save/data:/var/www/opentrashmail/data hascheksolutions/opentrashmail:1

Complete example with running as daemon, persistence, a domain for auto-generation of emails, acceptng only emails for configured domains, cleanup for mails older than 90 days and auto restart

docker run -d --restart=unless-stopped --name opentrashmail -e "DOMAINS=mydomain.eu" -e "DATEFORMAT='D.M.YYYY HH:mm'" -e "DISCARD_UNKNOWN=false" -e "DELETE_OLDER_THAN_DAYS=90" -p 80:80 -p 25:25 -v /path/on/host/where/to/save/data:/var/www/opentrashmail/data hascheksolutions/opentrashmail:1

How it works

The heart of Open Trashmail is a Python-powered SMTP server that listens on incoming emails and stores them as JSON files. The server doesn't have to know the right email domain, it will just catch everything it receives. You only have to expose port 25 to the web and set an MX record of your domain pointing to the IP address of your machine.

Webhook Configuration

OpenTrashmail supports both global and per-email webhooks for maximum flexibility:

Quick Start

1. Via Web UI: Click "Configure Webhook" on any email address page
2. Via API: POST /api/webhook/save/email@example.com with your configuration

Features

Per-Email Webhooks

• Custom endpoint URL for each email address
• Customizable JSON payloads with template placeholders
• Automatic retry with exponential backoff (max 10 attempts)
• HMAC-SHA256 signature for security
• Simple web interface configuration

Payload Template Placeholders

Placeholder	Description	Example
{{to}}	Recipient email	test@example.com
{{from}}	Sender email	sender@domain.com
{{subject}}	Email subject	Hello World
{{body}}	Plain text body	Email content...
{{htmlbody}}	HTML body	<p>Email content...</p>
{{sender_ip}}	Sender's IP	192.168.1.100
{{attachments}}	Attachment array	[{"filename":"doc.pdf","size":1024}]

Example Configuration

{
  "email": "{{to}}",
  "from": "{{from}}",
  "subject": "{{subject}}",
  "body": "{{body}}",
  "attachments": {{attachments}}
}

Note: {{attachments}} outputs a JSON array - don't wrap it in quotes.

API Reference

Endpoint	Method	Description
/api/webhook/get/[email]	GET	Get webhook configuration
/api/webhook/save/[email]	POST	Save webhook configuration
/api/webhook/delete/[email]	DELETE	Delete webhook configuration

Save Webhook Example

curl -X POST http://localhost:8080/api/webhook/save/test@example.com \
  -d "enabled=true" \
  -d "webhook_url=https://myapi.com/webhook" \
  -d 'payload_template={"email":"{{to}}","subject":"{{subject}}"}' \
  -d "max_attempts=5" \
  -d "secret_key=your-secret-key"

Security: Verifying Webhook Signatures

When a secret key is configured, OpenTrashmail includes an X-Webhook-Signature header with each request containing the HMAC-SHA256 signature of the request body.

Verification Examples

PHP:

$payload = file_get_contents('php://input');
$signature = $_SERVER['HTTP_X_WEBHOOK_SIGNATURE'] ?? '';
$expected = hash_hmac('sha256', $payload, 'your-secret-key');

if (!hash_equals($expected, $signature)) {
    http_response_code(401);
    exit('Invalid signature');
}

Python:

import hmac
import hashlib

def verify_webhook(request):
    payload = request.body
    signature = request.headers.get('X-Webhook-Signature', '')
    expected = hmac.new(
        b'your-secret-key',
        payload,
        hashlib.sha256
    ).hexdigest()
    
    if not hmac.compare_digest(expected, signature):
        return HttpResponse('Invalid signature', status=401)

Node.js:

const crypto = require('crypto');

function verifyWebhook(req, res) {
    const signature = req.headers['x-webhook-signature'];
    const expected = crypto
        .createHmac('sha256', 'your-secret-key')
        .update(req.rawBody)
        .digest('hex');
    
    if (signature !== expected) {
        return res.status(401).send('Invalid signature');
    }
}

Testing

Use the included test script for quick verification:

# Simple test
python3 tools/test_webhook.py test@example.com --send-email

# With signature verification
python3 tools/test_webhook.py test@example.com --secret "your-secret-key" --send-email

Limitations & Security

• Webhook URLs cannot point to localhost or private IP ranges (SSRF protection)
• Maximum 10 retry attempts to prevent resource exhaustion
• Payload templates must be valid JSON
• All placeholders are properly escaped to prevent JSON injection