Spark vs. Mozilla Thunderbird

Comparison of Spark and Mozilla Thunderbird
Real cost
	Spark A modern inbox that sorts what matters first. Your mail passes through the vendor's servers.	Mozilla Thunderbird A free, open-source client for any number of accounts, with strong privacy. It looks plainer than rivals.
Price	60 € per year	0 €
Payment	Subscription	Free
Trial	No trial	No trial
Free Tier	Free plan with the core mail features	No free tier
Open Source	No	Yes
Features and limits
Main Features	Smart inbox that sorts mail by importance Snooze and send later Shared inboxes for teams Writing help Unified inbox	Unlimited mail accounts Calendar and contacts Add-ons Strong privacy settings Message filters and tags
Limits	Mail is processed on the vendor's servers The best features need a paid plan	Setup of some accounts takes a few steps The design is plainer than rivals
Compatibility and trust
Supported Operating Systems	WindowsmacOS	WindowsmacOS
Verified on	10 Sep 2026	3 Oct 2026
Where to buy
Vendor	Go to vendor’s site: Spark (opens in a new tab) Free plan; paid plan per year. Approximate list price in euros, check the vendor.	Go to vendor’s site: Mozilla Thunderbird (opens in a new tab) Free, open source.

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