Microsoft Exchange Online

Judgement

What it is

Complete system

What it does

Microsoft's hosted email, calendar and contacts server, used through Outlook, with shared mailboxes, retention policies and compliance tools.

Adopt it when

An organisation uses Outlook and Microsoft 365 and needs shared mailboxes, resource calendars and compliance controls.

Watch out

Administration is complex, and security defaults need deliberate tuning to avoid compromised accounts.

Ready for

Production-ready

Runs as

Cloud service

What the license allows

Closed source: you use it under the maker's terms and cannot change or resell the code.

Judged on 2026-11-03 from the maker's description and Wikipedia. The license and age lines are worked out directly.

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Every alternative to Microsoft Exchange Online

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3. 3
   Fastmail Fastmail Pty Ltd

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   Complete system Production-ready A small business wants low-cost email on its own domain, particularly if it uses other Zoho apps.

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Under it

Every program, Microsoft Exchange Online included, runs on a microchip.

How compilers were built, back to punched paper tape