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Email Clients4 alternatives

Alternatives to Outlook

Microsoft's email client.

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What is Outlook?
Outlook is Microsoft's email and calendar client, available as a web app, desktop app and mobile app.
What does it do?
Reads and sends mail across Microsoft 365, Exchange and IMAP accounts, with rules, folders, search and shared mailboxes. Bundles calendar, contacts and tasks, and connects to Teams and other Microsoft 365 apps.
Who is it for?
People inside a Microsoft 365 organisation, where calendar and directory integration is the whole point. Those outside that ecosystem often prefer a lighter client.
What are the alternatives to Outlook?
Spark and Superhuman are triage-focused clients that sit on top of existing accounts, while Fastmail and Proton Mail are full email providers, with Proton emphasising end-to-end encryption.

Top alternatives

Smaller, founder-led tools that quietly compete with Outlook.

Spark website preview

Smart email.

A third-party client you point at existing accounts, strongest on iOS and Mac.

Superhuman website preview

Premium AI email.

Trades Outlook's breadth for one narrow goal: getting through the inbox quickly.

Fastmail website preview

Independent paid email.

Independent and ad-free, with strong IMAP support and custom domain handling.

Proton Mail website preview

Encrypted email.

End-to-end encrypted mail hosted in Switzerland, under Swiss privacy law.

4 alternatives to Outlook (2026) · Startup Alternatives