Microsoft 365 vs mailcow: dockerized

Fit:

Migration notes

Replaces custom-domain mailbox hosting, not the full office suite. Mailcow sync jobs copy messages from IMAP; calendars, contacts, permissions and client behavior need separate migration checks. Operator manages DNS, deliverability, backups and upgrades.

Sources: docs.mailcow.email, docs.mailcow.email, www.microsoft.com · checked 2026-10-21

Microsoft 365Paid incumbent

Entry priceUSD 5.40 / seat / month

Pricing modelper-seat, billed annual

OwnerMicrosoft Corporation

Business Basic without Teams USD $5.40/user/month paid yearly; web/mobile apps. Basic with Teams $7; desktop apps require another plan. Source

Microsoft 365 plans reviewed
Business Basic (no Teams)	entry	USD 64.80 / user / yr
Business Standard with Copilot	business	USD 282 / user / yr
Microsoft 365 E7	enterprise	USD 1,188 / user / yr

mailcow: dockerizedOpen-source alternative

Fit for Microsoft 365

License

GNU General Public License v3.0 Permissions of this strong 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. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changesDisclose sourceSame license No LiabilityWarranty Summary from GitHub's choosealicense.com

Paid-feature tier A

Self-host

Paid-feature limitsNone established

mailcow: dockerized plans reviewed
mailcow: dockerized	free self-hosted core	Free
managed mailcow base package (12 months)	vendor commercial managed hosting	USD 625.92 / dedicated managed server / yr
Custom managed mailcow	vendor commercial managed hosting	Quote only

What you may give up

No paid-feature limits established for this edition.

Server resources, DNS, backups, upgrades and mail delivery reputation remain operator responsibilities; paid managed hosting/support are optional services.

Tier A: GPLv3 orchestration and mailcow UI with an integrated mail/groupware stack. Reviewed documentation exposes administration, spam controls, SOGo and mailbox migration without an edition paywall; Servercow sells hosting and support rather than a separate gated software edition. Bundled components retain their own licenses. License source

What running it takes

Postfix and Dovecot
Rspamd, Unbound and Netfilter

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

Default complete dockerized deployment includes SQL, Redis, web/groupware, SMTP/IMAP, antispam and DNS containers; no mandatory external database/cache. Host Docker requirements distinct from bundled runtimes. ClamAV and FTS explicitly optional. Reviewed current stable-family docs and current Compose, not a source build. Infrastructure and staff time are not priced here; this page does not compare total cost.