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Open sourceTools & open source2026

HloolMail

Self-hosted temporary mail.

Self-hosted temporary mail and custom-domain inboxes for teams, tests and AI agents.

Type: Open-source platform
GitHub: 126+ stars
Stack: Go · PostgreSQL / SQLite
Deploy: Docker · Linux / macOS / Windows

Overview

HloolMail receives mail for any domain you own. Point your MX records at it and every address — even on wildcard subdomains — lands in a web console, an API, a webhook or a read-only share link.

The problem

Sign-up tests, CI pipelines and AI agents all need real inboxes for verification codes. Public disposable-mail services are unreliable and leak data, while a full mail server is overkill for receive-only needs.

How it works

01 / 03
Receive-only by design: an SMTP catch-all for your domains, including wildcard subdomains — no outbound mail and no IMAP or POP3, which keeps the attack surface small.
02 / 03
Built for automation: API keys, an endpoint for polling the next verification code, signed webhooks with retries, a built-in CLI and auto-generated OpenAPI docs.
03 / 03
Easy to run: a Go binary with the web console embedded, Docker Compose with PostgreSQL or SQLite, a first-run install page, per-user isolation, HTML sanitisation and optional Prometheus metrics.

What it does

Catch-all receiving

SMTP catch-all on your own domains, with wildcard subdomain mailboxes.

Web console

Manage inboxes, domains, API keys, webhooks and share links in one place.

Code polling API

Scripts and AI agents fetch the next verification code with one call.

Signed webhooks

message.received events delivered with signatures and retries.

Share links

Read-only mailbox access through an unguessable token and access key.

CLI & OpenAPI

A built-in CLI and generated API docs in JSON, YAML and Markdown.

Inside the interface.

signup-7f3a@qa.example.devRandom addressWebhookconnected

Inbox12Live

A
Acme IDnow
Your verification code
signup-7f3a@qa.example.dev
H
Harbor1m
Confirm a new device
agent-11@bots.example.dev
A
Atlas Shop3m
Security check
buyer-4@qa.example.dev
T
Tandem8m
Password reset code
ci-213@build.example.dev
K
Kestrel15m
Your sign-up code
signup-91c2@qa.example.dev
N
Northwind26m
Your 2-step code
agent-07@bots.example.dev
L
Lumen41m
Confirm your email
test+lumen@qa.example.dev
O
Orbit Pay1h
One-time passcode
ci-212@build.example.dev
N
Nimbus Cloud2h
Your sign-in code
agent-02@bots.example.dev

Your verification code

Acme ID <no-reply@acme.example>

To signup-7f3a@qa.example.dev

09:41

PreviewHTMLRaw

Acme ID

Hi there,

Your verification code is:

482913Copy

It expires in 10 minutes. Don't share it with anyone.

This is an automated message — please don't reply.

HTML sanitisedRead-only share link

DesktopInterface illustration

Project details

Our role: Designed, built and maintained as open source.
Platforms: Self-hosted · Docker · binaries
Stack: Go
Vite
PostgreSQL
SQLite
SMTP
Docker
OpenAPI
Source code: github.com/hloolx/HloolMail(opens in a new window)
First release: 2026

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Open source

Let's build the next HloolMail.

From first sketch to running in production — we build your product to the same standard as our own.

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Key facts