Every reply. Every tool. One inbox.
MasterInbox is a reply-management layer that sits on top of outbound sequencers rather than replacing them. It pulls responses from email and LinkedIn tools - SmartLead, Email Bison, Instantly, HeyReach, Expandi, Aimfox - into one view, stitches them into a per-prospect "Master Thread" spanning campaigns and subject lines, applies AI labels such as Lead, Demo, Objection and Interested, and organises everything into client workspaces with access controls.
The API details below are not linked to a current official developer page. Confirm them with the vendor before implementation.
| Plan | Price | Included | Notable |
|---|---|---|---|
| Growth | $349 / month | 1,500 mailboxes; 10 workspaces | Warm up auto sync, AI Labeling |
| Agency | $579 / month | 3,000 mailboxes; 30 workspaces | Everything in Growth, HeyReach integration, Expandi integration |
| Unlimited 30k | $1,497 / month, marked "limited time only" and asterisked | 30,000 mailboxes; unlimited workspaces | Everything in Agency, Unlimited Expandi, Unlimited HeyReach |
Checked 2026-08-07 against their pricing page. Vendors change pricing without notice.
MasterInbox addresses a specific operational failure in multi-mailbox outbound: replies arriving across dozens or hundreds of mailboxes and several sequencers, with thread context fragmenting across campaigns. Its unit of scale is the mailbox, not the seat - plans are sized at 1,500, 3,000 and 30,000 mailboxes, with workspace counts alongside (10, 30, unlimited). The vendor positions itself explicitly as an alternative to general shared-inbox tools like Front and Missive, and its self-described customers are outbound agencies managing reply handling for clients. Integrations are tiered: HeyReach, Expandi and Aimfox appear only from the Agency plan, and HubSpot plus API and webhooks only on the top plan.
Outbound agencies and GTM/RevOps teams running high-volume multichannel sequences across many client mailboxes, where reply handling is a staffed operational function rather than an individual rep's inbox. The vendor's framing is agencies whose clients churn over missed replies.
The entry price is $349/month for 1,500 mailboxes, and there is no smaller plan - a single team running a handful of mailboxes would be paying agency rates for capacity it cannot use, and no free tier or trial was documented. LinkedIn coverage is also gated: HeyReach, Expandi and Aimfox integrations start at the $579/month Agency plan, so the email-plus-LinkedIn unification that is the product's headline is not available on the entry tier. API access, webhooks and the HubSpot integration are top-tier only at $1,497/month, which puts programmatic use and CRM sync out of reach for anyone below that. And this is not a sequencer: you still pay for SmartLead, Instantly, HeyReach or whatever is sending, so MasterInbox is an additional line item on top of an existing stack.
No curated rival set covers this tool yet, so these are simply other tools in the same architectural layer and product form. Treat it as a starting point, not a shortlist.
Reply capture and context across many mailboxes. The vendor's stated case is that sequencers miss replies or lose thread context; MasterInbox consolidates email and LinkedIn responses into a single Master Thread per prospect that spans campaigns and subject lines.
The vendor names SmartLead, Email Bison, Instantly, Luella, HeyReach, Expandi and Aimfox. Note that HeyReach, Expandi and Aimfox integrations are listed only from the Agency plan ($579/month) upward.
Yes per the vendor - Email Bison and HeyReach can run simultaneously in one unified workspace, and you can filter by channel or build custom views to keep them separate while staying in one system. AI and manual labels apply consistently across both.
Per the vendor, agents that operate across selected channels to produce automated or drafted responses to both email and LinkedIn replies. They appear on the Agency plan with an asterisk and become unlimited on the top tier; we could not retrieve what the asterisk qualifies.
HubSpot is supported directly - replies, thread context and labels are pushed in - but the HubSpot integration is listed only on the top "Unlimited 30k" plan. Salesforce is supported indirectly through a stated partnership with OutboundSync offering attribution-based integration.
Replies appear in real time in the unified workspace, and the vendor states it can trigger instant Slack notifications for important or high-intent responses.
Yes - the vendor lists automatic exclusion of warm-up and unwanted email as part of its views-and-filters capability, which matters given the mailbox counts these plans assume.
API access and unlimited webhooks are listed as top-tier features.
We found none. Every path on the site is a demo booking, a paid signup, or a waitlist link in the pricing-page footer. The lowest documented commitment is $349/month.
This page tells you whether MasterInbox fits. Cheetah builds and runs the system it goes into — enrichment, sequencing, CRM and the joins between them.
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