Fastmail Business vs Stalwart Community

Fit:

Migration notes

Email/groupware scope only. Replaces standards-based email/calendar/contact hosting, not Google or Microsoft office apps and vendor automation. Pilot IMAP/CalDAV/CardDAV migration and client behavior; vendor service migration claims do not establish a turnkey Google Workspace or Exchange Online migration. Recovery and AI mail features require Enterprise. Source-account IMAP/export access must be enabled (Zoho Free excludes IMAP); pilot mailbox, calendar and contact transfer separately.

Sources: www.stalw.art, www.stalw.art, www.fastmail.com · checked 2026-10-21

Fastmail BusinessPaid incumbent

Entry priceUSD 3 / seat / month

Pricing modelper-seat, billed annual

OwnerFastmail

Basic USD 3/user/month billed yearly ($36/user/year); custom domains require at least one Standard or Professional user (Standard USD 5/user/month annually). Basic lacks third-party mail-client access; compare actual account mix. Source

Fastmail Business plans reviewed
Business Basic	entry	USD 4 / user / mo
Business Standard	popular	USD 6 / user / mo
Business Standard	business	USD 6 / user / mo

Stalwart CommunityOpen-source alternative

Fit for Fastmail Business

License

GNU Affero General Public License v3.0 Permissions of this strongest copyleft license are conditioned on making available complete source code of licensed works and modifications, which include larger works using a licensed work, under the same license. Copyright and license notices must be preserved. Contributors provide an express grant of patent rights. When a modified version is used to provide a service over a network, the complete source code of the modified version must be made available. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changesDisclose sourceNetwork use is distributionSame license No LiabilityWarranty Summary from GitHub's choosealicense.com

Paid-feature tier C

Self-host

Paid-feature limits3 noted

Stalwart Community plans reviewed
Community	free AGPL self-hosted core	Free
Enterprise (25–499 mailboxes band)	paid self-hosted Enterprise license	USD 2.40 / mailbox-year in first pricing band / yr
Enterprise (100,000+ mailboxes)	paid self-hosted Enterprise license	Quote only

What you may give up

Enterprise license required for deleted-email restoration and account archiving/un-deletion.
Enterprise-only AI/LLM spam classification and Sieve scripting; standard rule/statistical spam filtering remains Community.
Additional enterprise administration includes multi-tenancy, SCIM provisioning, advanced telemetry and sharded/read-replica storage.

Future first-party managed service announced with registration of interest; current general availability, regions and numeric SLAs not confirmed. Self-hosted infrastructure and delivery operations still cost money.

Tier C: Community source is AGPL-3.0-only, with per-file dual licensing and proprietary SEL enterprise sections. C because recovery and AI-assisted mail workflows require Enterprise, beyond administrative extras. Optional first-party managed hosting is announced, not confirmed generally available. License source

What running it takes

Stalwart server binary

RocksDB (embedded)
or
or
or
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FoundationDB

Hover or focus an icon for its name. Dashed means not established; struck through means no; grouped icons are alternatives.

Verified explicit single-node RocksDB default; structured data/blob/search/in-memory stores independently configurable. Redis, SQL, object storage and external search are alternatives rather than universal prerequisites. External auth/AI services optional; Enterprise AI features are not required by Community. Native installer distinct from Docker. Infrastructure and staff time are not priced here; this page does not compare total cost.