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GMass vs Mailbutler: catalog facts
GMass	Mailbutler
Freemium Paid plans are offered; check the developer's site for current pricing and free limits.	Paid Subscription service with a 14-day free trial.
Web, Browser extension	macOS, Browser extension
Works inside Gmail with no separate mail platform Unlimited automatic follow-up stages	Works inside Apple Mail and Gmail Mail merge with scheduled sending
Tied to Gmail and Google Workspace accounts Chrome extension only, according to the research	Email tracking reveals recipient activity, which some recipients object to Requires a subscription after the trial
Browser extension	Downloadable app, Browser extension
Closed source	Closed source
License not stated	License not stated
Account needed	Account needed
Needs internet	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

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