Microsoft Outlook vs. Mozilla Thunderbird

Comparison of Microsoft Outlook and Mozilla Thunderbird
Real cost
	Microsoft Outlook The standard for work mail, with calendar and contacts built in. The free version shows ads.	Mozilla Thunderbird A free, open-source client for any number of accounts, with strong privacy. It looks plainer than rivals.
Price	0 €	0 €
Payment	Free	Free
Trial	No trial	No trial
Free Tier	Free with ads; without ads as part of Microsoft 365	No free tier
Open Source	No	Yes
Features and limits
Main Features	Mail, calendar and contacts in one app Works with Microsoft 365 and Exchange Focused inbox Rules and categories Several accounts	Unlimited mail accounts Calendar and contacts Add-ons Strong privacy settings Message filters and tags
Limits	The free version shows ads The new version lacks some features of the classic one	Setup of some accounts takes a few steps The design is plainer than rivals
Compatibility and trust
Supported Operating Systems	WindowsmacOS	WindowsmacOS
Verified on	9 Oct 2026	3 Oct 2026
Where to buy
Vendor	Go to vendor’s site: Microsoft Outlook (opens in a new tab) Free with ads; part of Microsoft 365 without ads.	Go to vendor’s site: Mozilla Thunderbird (opens in a new tab) Free, open source.

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