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Thunderbird vs eM Client: catalog facts
Thunderbird	eM Client
Free Free forever, funded by donations.	Freemium Free licence for personal, non-commercial use with up to two accounts; Personal from…
Windows, macOS, Linux, Android	Windows, macOS, Android, iOS
Unified inbox across every account, or each account kept separate, your choice Mail, calendar, contacts and tasks in one application rather than four	Handles Gmail, Microsoft 365, Outlook, Exchange and plain IMAP without plugins Email, calendar, tasks, contacts, notes and chat in one polished window
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	No Linux version The free licence is capped at two accounts and forbids any commercial use
Downloadable app	Downloadable app
Open source	Closed source
License: MPL-2.0	License not stated
No account needed	Account needed
Works offline	Works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked September 20, 2026

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