Overview

The API handles sending and receiving across channels, while the inbox groups a thread’s messages and sorts threads by recent activity. Automatic routing can choose a channel based on the recipient and the sender’s configured channels, a practical way to centralize channel selection in an application rather than maintain it message by message.

This is an API-led product, not simply a shared mailbox. Its range of channels and customer-owned tools gives teams room to build tailored communication workflows, but teams looking for a conventional support desk should weigh that implementation focus against their need for a turnkey operation.

Key features

Channels, threads and routing

Supported channels include WhatsApp, SMS, one-way SMS, voice, email, Telegram, Instagram and Messenger. Threads bring messages from a contact’s channels together, and recent activity determines their order. The breadth helps applications reach customers through different channels; however, the free plan connects only two channels, and its monthly message allowance covers just WhatsApp, Telegram, Instagram and Messenger.

Agents and integrations

Agents can respond over messaging channels and phone, draw on agent-specific knowledge bases and memory, and call tools owned by the customer. That is useful for teams building agents around their own systems, rather than expecting a finished support workflow out of the box. TypeScript, Python, Ruby, Go and PHP SDKs are available, along with an MCP server, agent skills, CLI, n8n node and Vercel Marketplace integration. Zapier, Make, HubSpot, Salesforce, Shopify, WooCommerce, Zendesk, Intercom and GitHub are marked as coming soon.

Webhook security and sending

Webhooks use an X-Zavu-Signature HMAC signature; v2, which signs the timestamp together with the body, is the default for new senders. Sending stops when prepaid balance reaches zero, but inbound messages and webhooks continue. That separation preserves incoming activity while requiring teams to keep a close eye on their sending balance.

Pricing

Zavu is open source and offers a free plan, but free access has concrete limits. The Free Plan costs 0.00 USD per free and is billed Free forever. It includes two channel connections, 2,000 shared monthly messages across WhatsApp, Telegram, Instagram and Messenger, and $2 usage credit per month. That is a useful starting point for a small integration, but the shared quota and connection cap make it a constrained choice for broader production traffic.

Pro costs 20.00 USD per month, billed Monthly. It includes $20 monthly usage credit, unlimited channel connections, 2M memory units per month and prepaid usage. This is the more natural plan for developers who have outgrown the free caps and want room to connect more channels; prepaid usage still means sending can stop once the balance is exhausted.

Managed costs 1250.00 USD per month, billed at 50% off launch pricing; the normal price is $2,500 per month. It adds weekly conversation review, ongoing tuning and 24/7 support with a 30-minute response SLA, fitting teams that want ongoing operational help rather than only API access. Build costs 2450.00 USD per once, billed at 50% off launch pricing; the normal price is $4,900. It covers an agent designed, built and shipped in the customer’s Zavu account over four to six weeks, making it a one-time implementation option rather than a monthly service plan.

Enterprise has custom pricing, postpaid invoicing with NET-30, negotiated rates, multi-zone redundancy and an uptime SLA, plus a named engineer. It is aimed at organizations that need negotiated commercial terms and operational assurances. There is no free trial. Voice agents start at $0.07 per minute; premium models and voices cost extra, and BYOK is unavailable for voice agents. Teams using voice should account for those charges separately from plan pricing.

Platforms

Zavu supports API and web access. It is a fit for application builders who can work through an API and a web inbox, rather than teams whose choice depends on native mobile or desktop apps.

Who it's for

Choose Zavu if you are building a product or service that needs cross-channel messaging, configurable routing, or agents that can use customer-owned tools. Its SDK coverage and API-centered design suit engineering teams with a specific workflow to implement. Look elsewhere if your priority is a conventional shared inbox or support suite with broad ready-to-use integrations and a predictable fixed allowance for messaging.

Pros and cons

Pros

Eight supported channel types, with threads combining activity across a contact’s channels.
Automatic routing and customer-owned agent tools give application teams control over custom workflows.
Pro removes the channel-connection cap and includes $20 monthly usage credit for 20.00 USD per month.
Webhook signatures and a default timestamp-and-body signing mode provide a defined mechanism for verifying webhook requests.

Cons

The free plan limits users to two connections and 2,000 shared monthly messages across four named channels.
Prepaid balance exhaustion halts sending, even though inbound messages and webhooks continue.
Voice agents start at $0.07 per minute, with extra charges for premium models and voices and no BYOK option.
Several familiar service and commerce integrations remain marked as coming soon.

Alternatives

Browse shared inbox software if you are comparing products built around a shared mailbox rather than an API-led messaging workflow.

Zoho TeamInbox is worth considering for a team that wants shared incoming and outgoing channels, rules, internal discussions and draft sharing; its Starter plan has custom pricing.
Help Scout may suit a small support team wanting a defined free allowance: its free plan includes five users, one Inbox, one Docs site, 100 contacts per month, 10 saved replies and 10 tags.
Coherence offers a free plan with three users, 50 shared AI credits per month and 2,500 records, making it an option for readers comparing AI-oriented software with a free entry tier.
Trengo is a paid alternative with a free trial; its Boost plan costs 299.00 EUR per month billed annually and includes 10 users and 6,000 conversations per year.
Drag may fit teams that want a shared inbox inside Gmail, with Kanban, list and preview board views; its Starter plan costs 16.00 USD per month billed monthly.
Loop Email is another paid option, with a Starter plan at 18.75 USD per month billed monthly.
MailStack is an open-source alternative for readers who prefer a self-hosted, single-node reference deployment.
Maxdesk may suit teams looking for a free web-based ticketing option, with unlimited agents and tickets within fair usage.

Verdict

Zavu Inbox is a strong fit for developers who want one API and inbox for multi-channel conversations, routing and custom AI agents. Its range of channels, SDKs and agent capabilities is the main reason to choose it; the free-tier caps, prepaid sending behavior and metered voice costs are the reasons to look elsewhere if you need a ready-made help desk or tightly predictable usage.

	Sharebox	Zavu Inbox
Free plan	Yes	Yes
Free trial	No	No
Paid from	$79/mo	$20/mo
Open source	No	No
Platforms	Web	api, Web
Free plan	Yes	—
Mail platforms	gmail	standalone
Mobile apps	No	—
Internal comments	—	Yes

Sharebox vs Zavu Inbox

Sharebox

Zavu Inbox