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