Suggest a tool

Best / Email servers

Best open-source Email servers

The best self-hosted mailbox split in the c17.io catalog is Mailcow for a GPL-3.0 docker-compose groupware box (the published Outlook/Superhuman stack), Stalwart when you want one Rust binary (AGPL-3.0 core; skip SELv2; GitHub license field unset), Mail-in-a-Box when you want that CC0-1.0 one-box installer, and Postal when the job is mail delivery rather than a mailbox. Thunderbird stays on the laptop. Consumer Gmail stays on /replace/gmail. You still need a public IP, MX, and rDNS. This is not Outlook Copilot or Superhuman's AI inbox.

Open the stackStart on Railway

Ranked picks

  1. 1

    Mailcow

    GPL-3.0 dockerized mail server — the c17 Outlook/Superhuman path. /compare/mailcow-vs-mail-in-a-box.

    When to pick it: IMAP/JMAP mailboxes plus a SOGo-shaped UI.

    13,685 stars in the catalog

  2. 2

    Stalwart

    AGPL-3.0 core IMAP/JMAP/SMTP (skip SELv2). GitHub license Other — /compare/stalwart-vs-mailcow.

    When to pick it: One Rust binary if you skip SELv2.

    15,283 stars in the catalog

  3. 3

    Mail-in-a-Box

    CC0-1.0 one-box installer — /compare/mailcow-vs-mail-in-a-box.

    When to pick it: A machine you are willing to let the installer own.

    15,449 stars in the catalog

  4. 4

    Postal

    MIT mail delivery platform already in the catalog. Not a mailbox.

    When to pick it: Sending and receiving at the MTA layer, not Outlook.

    16,871 stars in the catalog

How they compare

ToolLicenseSelf-hostBest for
MailcowGNU General Public License v3.0MediumIMAP/JMAP mailboxes plus a SOGo-shaped UI.
StalwartOtherMediumOne Rust binary if you skip SELv2.
Mail-in-a-BoxCreative Commons Zero v1.0 UniversalMediumA machine you are willing to let the installer own.
PostalMIT LicenseHarderSending and receiving at the MTA layer, not Outlook.

Related pages

FAQ

Mailcow or Stalwart?
Mailcow if you want the published Outlook path. Stalwart if you want one Rust binary — skip SELv2. /compare/stalwart-vs-mailcow.
Where does Thunderbird run?
On the laptop. This page is the mailbox. Superhuman is a client; Thunderbird is the client you keep.
Is this Gmail?
Gmail stays on /replace/gmail (Mailflare / Stalwart). This page is Outlook/Superhuman.
Why is Postal last?
Postal delivers mail. It is not a mailbox you open in Thunderbird.
Are these free?
Mailcow is GPL-3.0. Stalwart core is AGPL-3.0 if you skip SELv2. Mail-in-a-Box is CC0-1.0. Postal is MIT. You pay the VPS and IP reputation.
How do I deploy it?
Open /stacks/mailcow-mailbox. A VPS with MX and rDNS is the honest path. Create one mailbox and point Thunderbird at it.

Stack of the Week

Get one stack a week that replaces a SaaS bill.

Sponsor this page