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Thunderbird vs Kiwi for Gmail: catalog facts
Thunderbird	Kiwi for Gmail
Free Free forever, funded by donations.	Paid Paid after a free trial, and can be cancelled at any time.
Windows, macOS, Linux, Android	Windows, macOS
Unified inbox across every account, or each account kept separate, your choice Mail, calendar, contacts and tasks in one application rather than four	Gmail and Google Workspace in dedicated desktop windows Quick access to Docs, Sheets, Slides and Drive
The interface carries a lot of history and can feel dense next to a webmail tab Major ESR releases have historically been disruptive for add-ons and settings	Only works with Gmail and Google Workspace Paid after the trial
Downloadable app	Downloadable app
Open source	Closed source
License: MPL-2.0	License not stated
No account needed	Account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.