Can I open-source Fastmail?
YES · mature open-source replacementYes. Listmonk (22k stars), Mailspring (18k stars), Stalwart (8k stars) are mature open-source replacements for Fastmail — self-host in one command and stop paying $6/mo.
People still pay for Fastmail because an email client can be rebuilt; operating a trusted mail service with excellent deliverability cannot. The recurring cost buys IMAP quirks, OAuth, MIME, threading, search, attachments, offline sync, notifications, secure storage, and provider changes, not just the visible interface.
xmail hosting, spam filtering, domains, calendars, contacts, deliverability, and support
xmail hosting and deliverability
xpush on every platform
xadvanced team collaboration
xprovider-specific AI and search
These projects already replace it, free.
MMailspringA fast unified desktop inbox with local search; workflow extras still cost money.open source↗SStalwartModern all-in-one mail server in Rust with JMAP, IMAP, and SMTP plus built-in spam filtering.open source↗TThunderbirdA mature client for almost any mailbox; the interface has survived more redesign cycles than most startups.open source↗What each one is, in full: Stalwart
all 4 open-source alternatives to Fastmail →· no votes, no pay-to-list · just what's real
Fastmail pricing
| plan | monthly | annual (per mo) | what you get |
|---|---|---|---|
| individual | $6/user | $5/user | 1 user; 60 GB total storage (50 GB mail/calendar/contacts + 10 GB files). |
| duo | $10 | $8 | 2 users; 120 GB total storage (60 GB per person). |
| family | $14 | $11 | Up to 6 users; up to 360 GB total storage (60 GB per person). |
| basic (business) | $4/user | — | 6 GB per user (5 GB mail/calendar/contacts + 1 GB files). |
| standard (business) | $6/user | — | 60 GB per user (50 GB mail/calendar/contacts + 10 GB files). |
| professional (business) | $10/user | — | 150 GB per user (100 GB mail/calendar/contacts + 50 GB files). |
free tierno free tier; up to 30-day free trial
billingmonthly, annual, 24-month and 36-month prepayment; personal annual rates shown above; cancel/change anytime, but unused prepaid time is not refunded
hidden costsTaxes are extra; paid storage upgrades are available up to 300 GB per user but public add-on prices were not shown; registering a custom domain costs extra if you do not already own one.
verified 2026-08-12 · source ↗
Can I open-source Fastmail?
Yes. Mailspring replaces Fastmail today — self-host it on your own server or machine with no subscription. The full list of open-source alternatives is on this page.
How much does Fastmail cost?
Fastmail costs about $6/month (Individual, checked 2026-07-31), which is $72 per year. That's what you save by replacing it with open source.
What do I lose by replacing Fastmail?
Honestly: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support; mail hosting and deliverability; push on every platform; advanced team collaboration; provider-specific AI and search. If any of those are load-bearing for you, keep paying.
Is there an open-source alternative to Fastmail?
Yes: Mailspring (A fast unified desktop inbox with local search; workflow extras still cost money.) Stalwart (Modern all-in-one mail server in Rust with JMAP, IMAP, and SMTP plus built-in spam filtering.) Thunderbird (A mature client for almost any mailbox; the interface has survived more redesign cycles than most startups.) All 4 curated open-source alternatives are at caniopensourceit.online/fastmail/alternatives.