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Mailstrom vs Inbox Zero: catalog facts
Mailstrom	Inbox Zero
Paid Paid service with a free trial that needs no credit card.	Freemium Free to start, with paid and sales-led plans for more use.
Web	Web
Bulk delete and unsubscribe across thousands of messages Works with Gmail and other providers	Automatic labelling and pre-drafted replies Bulk unsubscribe and cold email blocking
Requires granting a third-party service access to your mailbox Paid after the trial	Supports Google and Microsoft accounts only Mobile apps are not yet available
Hosted service	Web application, Hosted service
Closed source	Open source
License not stated	License not stated
Account needed	Account needed
Needs internet	Needs internet
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 1, 2026

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