Fastmail vs Mail-in-a-Box
Fastmail and Mail-in-a-Box are both email server software. Fastmail is a commercial product from Fastmail Pty Ltd. Mail-in-a-Box is open source under CC0-1.0, with 15k GitHub stars.
Which to pick
- Pick Fastmail when
- An individual, family or small business wants fast, private email on its own domain without Google or Microsoft.
- Pick Mail-in-a-Box when
- You want your own email on a dedicated VPS with as few decisions as possible.
Side by side
Paid, ad-free email hosting with calendars, contacts, custom domains and masked email addresses, built on open standards (IMAP, JMAP, CalDAV).
A setup script that turns a fresh Ubuntu server into a complete mail server with Postfix, Dovecot, Roundcube webmail, Nextcloud contacts and calendars, spam filtering, DNS and TLS.
No office suite or file storage included, and data is held in Australia and the US.
It takes over the whole machine, allows almost no customisation, and depends on a specific Ubuntu LTS release.
Production-ready (both)
Cloud service and mobile app
Self-hosted server
Not published
Python, Shell, Postfix, Dovecot, Roundcube and Nextcloud
Closed source, sold by Fastmail Pty Ltd
Open source, CC0-1.0 (public domain)
Closed source: you use it under the maker's terms and cannot change or resell the code.
You can take the code into anything, including a product you sell, with no conditions.
586 Wikipedia readers a month on phones
15k GitHub stars
Not known
Established: started 13 years ago, latest release v77.
Other comparisons
More email servers and webmail
Both sides were judged on 2026-11-03 from makers' descriptions, Wikipedia, READMEs and GitHub data. License, age and popularity lines are worked out directly.