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

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