MailStack

What MailStack is

MailStack is an open-source, self-hosted mail server and shared team inbox for business email that is meant to receive messages rather than send them. Its web inbox provides search, pagination, read states, attachment filters, message previews, live polling, and browser notifications. Administrator and ordinary-user accounts can access shared mailboxes, with object-level isolation between mailboxes. MailStack ingests messages through Maildir, guards against duplicate delivery, and can recover from malformed messages. It sanitizes HTML and blocks remote and active content; attachments remain in protected storage and are downloaded through authorized routes. Listed protections include Argon2 password hashing, login throttling, CSRF safeguards, secure production cookies, and least-privilege database access. The reference setup receives mail using Postfix and delivers it through Dovecot LMTP; it does not include public SMTP submission, IMAP, POP3, or open relay. It is designed for a single-node Ubuntu Server 24.04 LTS VPS with public DNS and reachable inbound ports 25, 80, and 443. The project also lists health checks, audit logs, and backup, restore, rollback, and verification tools. It is free under GNU AGPL version 3.0 or later.

Who it suits

MailStack is intended for teams that want self-hosted business inboxes with per-user shared mailbox authorization and controlled receive-only email. The supported reference deployment suits teams able to operate a single-node Ubuntu Server VPS.

Limits

The free Open source plan is a self-hosted, single-node reference deployment. That deployment excludes public user registration, outbound campaigns, multi-node or high-availability deployment, and a public administrative API; public SMTP submission, IMAP, POP3, and open relay are also excluded.

Getting started

1. Visit the MailStack product page.
2. Prepare a single-node Ubuntu Server 24.04 LTS VPS.
3. Configure public DNS and make inbound ports 25, 80, and 443 reachable.
4. Deploy the reference mail flow using Postfix for receiving mail and Dovecot LMTP for delivery.
5. Create administrator and ordinary-user accounts and set shared mailbox memberships.

Verdict

MailStack offers a focused receive-only shared inbox for teams that want to host and administer their own mail setup. Its single-node deployment requirements and lack of standard outbound and mailbox protocols are important constraints to weigh.