Resend Inboxes adds shared email for agents, with setup and permission limits

Email conversations become a shared workspace

Resend launched Inboxes on October 22, adding shared email conversations that applications, AI agents and people can work on together. Messages belong to threads, colleagues can assign work and leave notes, and developers can connect their own agents or configure Resend’s built-in agent.

The release is available to start using on the Free plan. Its practical addition is a common record of the conversation: an agent can prepare work that a person picks up in the same inbox. For teams building email assistants, the appeal is having conversation management supplied alongside delivery.

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Receiving email was already possible

Resend introduced its Inbound service in November 2025. That service could receive mail, parse content, store attachments and notify an application through a webhook—an event sent to a server when mail arrives. Developers could inspect received messages in the dashboard and retrieve attachments through an API.

Inboxes adds a conversation and collaboration layer to that foundation. Consider a hypothetical support request that needs a colleague’s decision: an assistant could organize the thread and prepare a response, while the colleague reviews the exchange. That illustrates the new shared workflow; it is not a result from our own testing.

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Forwarding changes the domain setup

An inbox uses an address on a domain added to Resend. The creation API requires verified DKIM and SPF, the domain records used for sending authentication. In the ordinary receiving setup, receiving must also be enabled and the inbound MX record must be verified or pending.

There is another route for an address whose mail already arrives elsewhere. Setting forwarding to true provisions a Resend receiving address without requiring a new MX record. The existing mailbox must then forward messages to that address. This offers a way to retain the existing mail destination, but does not remove the sending-authentication requirement.

The API also rejects an address already in use or a request that exceeds the team’s inbox allowance. Creating another address therefore depends on both domain readiness and plan capacity.

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Drafting and sending remain different operations

The built-in agent’s settings expose instructions, tone and an explicit action list. Documented actions include drafting a reply, forwarding a thread, adding labels, assigning work, marking spam, archiving and moving a thread to trash. The list contains no send-reply action. That distinction matters when reading the announcement’s broader language about agents responding to email.

Other interfaces can send: Resend’s MCP documentation lists thread replies and sending drafts among its inbox tools. A team must distinguish the built-in agent’s configured actions from the capabilities of an external agent connected to those tools.

Settings updates also have a consequential detail: a supplied actions list replaces the existing list. An empty list disables all those agent actions, while omitted settings retain their current values. Changing a tone alone is different from replacing what the agent may do.

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The connection determines what an agent can reach

Resend offers both hosted and local MCP servers, using the protocol that lets AI clients call external tools. However, its current tool documentation specifically limits Inboxes to the hosted remote server; the local resend-mcp package is not supported for these inbox tools. The hosted connection uses OAuth approval, with an API-key option for environments without browser login.

For a custom agent server, Resend’s official inbox skill documents a full-access API key for reading mail and registering webhooks. A sending-access key can reply, forward, create drafts and send drafts, but cannot read inbox messages or register webhooks. The guide warns that a full-access key can reach other projects in the account.

This is a separate boundary from the built-in agent’s action list. The same guide treats incoming mail as untrusted input and calls for webhook verification and restricted handling. Shared threads preserve conversation history; they do not make a sender’s instructions trustworthy.

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Three inboxes share the email allowance

The Free plan lists 3,000 emails a month and a daily limit of 100. Every message sent or received through an inbox counts toward the transactional quota; the three included inboxes do not each receive a separate allowance.

Pro starts at $20 a month for 50,000 emails. Additional inboxes on paid plans require pay-as-you-go to be enabled and cost $1 each per month. Resend also lists plan-specific AI-credit allocations, so mailbox count alone is not a complete description of the service’s usage limits.

The useful change is shared email state with several ways to act on it. The deployment decision still turns on which connection can access the inbox and how much authority the agent receives.

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