Agent Inbox

An agent inbox is a mailbox on a domain you own, such as support@inbox.yourdomain.com. Reloop receives mail for it, groups messages into threads, flags spam, and lets you send and reply from the same address. The same mailbox works for a person in the dashboard, for your code through the API, and for an AI agent through MCP.

How it works

Mail arrives. Your domain's MX record points to inbound.reloop.sh. Reloop accepts mail for every mailbox on that domain.
It is stored and threaded. Each message lands in its mailbox and is attached to a thread with the earlier messages in the conversation.
It gets a spam verdict. Every inbound message is scored. Messages scored as spam are still stored, with is_spam: true.
You are notified. An email.received webhook fires with the mailbox, sender, subject, thread and message IDs.
You reply in the thread. Replies are sent from the mailbox address and stay in the same conversation for the recipient.

Set up a mailbox

Add the domain and MX record

Add a domain with Email Receiving turned on, and publish the MX record inbound.reloop.sh. Use a subdomain if your root domain already receives mail elsewhere. See Receiving emails.

Create the mailbox

Create it from the domain page in the dashboard, with the Mailboxes API, or with the Node.js SDK:

const { mailbox, mailboxError } = await reloop.inbox.mailboxes.create({
  domainId: "dom_...",
  email: "support@inbox.yourdomain.com",
  displayName: "Acme Support",
});

Send it a test

Email the address from any personal account. The message appears in the mailbox within a few seconds.

Threads and messages

Concept	What it is
Mailbox	One address, such as `support@inbox.yourdomain.com`, with its own display name
Thread	A conversation. Status is `active`, `archived`, `closed` or `trash`, and threads can be starred, labelled and marked read
Message	One inbound or outbound email in a thread, with attachments and the raw source available
Draft and note	Unsent replies, and internal notes your team leaves on a thread

Load the whole thread before replying, so a person or model sees every earlier message, inbound and outbound.

Send and reply

Reply or reply all to a message to keep the conversation in one thread. Reloop sets the threading headers for you.
Forward a message to another address.
Send a new message from the mailbox.
Delay a send with scheduledAt, or give it an undo window with undoWindowSeconds. A pending send can be cancelled until it goes out.

The Messages API and the SDK (reloop.inbox.messages.reply, replyAll, forward, send, cancelPending) cover all of these.

Ways to work with an inbox

Method	Best for
Dashboard	People reading, replying, labelling and leaving notes
Webhooks	Reacting to each new message in your code. Subscribe to `email.received` and verify the signature.
API and SDKs	Listing threads, fetching messages, replying and sending (Threads, Messages)
MCP	Letting Claude, Cursor or another AI client read and answer mail. See MCP server.
IMAP	Apple Mail, Outlook, Thunderbird or any IMAP client

IMAP settings

Setting	Value
Host	`imap.reloop.sh`
Port	`993` (TLS) or `143` (STARTTLS)
Username	The mailbox address
Password	A Reloop API key from the mailbox's organization that is allowed to use that address

Restrict what an agent can reach

Give each agent an API key restricted to its own address or domain. A restricted key can only list, read, change and send from the mailboxes its scope allows. This applies to the whole inbox API, to sending, to SMTP and to IMAP login. Requests for any other mailbox return 403.

Treat inbound email as untrusted input. An email can contain instructions written to manipulate an AI agent, so do not let a model follow instructions found in a message, and require human approval before an agent sends anything consequential.

Limits

Each plan includes a number of agent inboxes:

Plan	Agent inboxes
Free	3
Pro	5
Growth	10
Enterprise	Custom

Creating or re-activating a mailbox beyond your plan's limit fails. Each mailbox has a 5 GB storage quota by default. Self-hosted Reloop has no inbox limit.