Mozilla Thunderbird vs. Microsoft Outlook

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

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