Gmass Inbox
Mass email, built into Gmail.
What is Gmass Inbox
GMass plugs directly into Gmail as a Chrome extension, letting users send mass email campaigns, run mail merges personalized from Google Sheets data, and schedule follow-up sequences — all from the Gmail compose window. It's built for SDRs, founders, and marketing teams at SMBs and mid-market companies who want outreach volume without switching to a separate platform. The standout capability is Inbox Rotation (MultiSend), which distributes a single campaign across multiple Gmail accounts to reduce per-account send pressure and improve deliverability. GMass also includes built-in email address verification and a Spam Solver tool to test deliverability before a campaign goes out. The hard constraint: GMass is Gmail-only, so if your team runs on Outlook or any non-Google mail stack, it's a non-starter.
Key features
schedules and delivers outbound sequences at scale
first-party connectors, no middleware required
multi-step sequences, event-driven triggers, A/B testing
fits any iPaaS or workflow chain
Vanderbuild take
GMass is a focused Gmail-native email sender — a practical pick for founders and SDR teams who live in Google Workspace and want outreach volume without onboarding a separate platform. On the agentic side, it's Capable: the REST API and webhooks give you enough surface area to wrap GMass into your own orchestration layer or MCP setup, though there's no native MCP server, so you'll be doing that wiring yourself. At $29.95/seat/month to start, it's affordable for small teams, but costs stack as you add seats and the sending limits tied to individual Gmail accounts can become a ceiling before your budget does. The Gmail-only constraint is the real filter here — if any part of your team is on Outlook or a custom mail server, GMass simply doesn't apply.
Agentic stack profile
APIRESTProgrammatic access available.
REST API — straightforward to call from any agent or workflow tool. Rate limits and auth vary by plan.
API docs →Agentic readinessCapableSolid API access — wraps cleanly for agent use.
Solid REST or SDK access. No MCP server yet, but easy to wrap in custom agent tooling. Most modern SaaS tools land here.
Stack roleSequencerWhere this tool slots into an agentic pipeline.
Plays the role of Sequencer in an agentic pipeline. Use it to send and track multi-step outbound cadences across channels.
Gmass Inbox alternatives
Tools that solve a similar problem — compared at a glance.
- Pricing
- Seat-based
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- $$
- Best for
- SDR / BDR, Founder
- Readiness
- Capable
- API
- REST
- Pricing
- Workspace-based
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- $$
- Best for
- SDR / BDR, Founder
- Readiness
- Native
- MCP
- Yes
- API
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- Pricing
- Freemium
- Budget
- $$
- Best for
- SDR / BDR, Agency
- Readiness
- Native
- MCP
- Yes
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- REST
Frequently asked questions
Does Gmass Inbox have a public API?
Yes — Gmass Inbox ships a REST API. Docs: https://api.gmass.co/docs.
How much does Gmass Inbox cost?
Gmass Inbox: pricing is seat-based, expect mid tier ($$) spend. Full pricing page: https://www.gmass.co/pricing.
Who is Gmass Inbox best for?
Gmass Inbox is built for SDR / BDR, Founder, Marketing. Fits SMB (1-50), Mid-market (50-500)-sized teams.
How well does Gmass Inbox fit an agentic sales stack?
Tier: Capable. Solid public API, no MCP yet — straightforward to wrap in your own agent tooling.