Sendmux: MCP server, CLI and agent surfaces

Sign-in required, tools not seen, not counted. The MCP endpoint listed for Sendmux at mcp.sendmux.ai answered 401 with OAuth metadata on 4 November 2026. Its tools can be listed only after a person authorizes a client, and this directory never signs in.

Fact sheet

Company	Sendmux (registry title: Email Inbox API + Sending by Sendmux)
Domain	sendmux.ai
Category	Uncategorised (assigned by this directory from the registry description)
MCP server	Sign-in required (OAuth with client registration)
Ora score	93, grade A; Ora scanned the domain on 27 October 2026 and the cached score was read on 5 November 2026 from its score API (Ora's score page for sendmux.ai, a vendor-published score)
Company found through	the GitHub MCP Registry
Last verified	4 November 2026

MCP server

Endpoint	`https://mcp.sendmux.ai/mcp`
How it was found	listed in the GitHub MCP Registry
Transport	streamable-http
HTTP status	401
Connected	4 November 2026, 20:04 UTC
Handshake time	618 ms over 1 attempt

The endpoint answered the handshake with a sign-in challenge, so the tool list is not visible to this directory. It is not counted as an MCP server: a sign-in challenge is its own state, and the connector listed no tools.

Connector log

2 connections on 4 November 2026, read-only methods only

19:59:24Z https://mcp.sendmux.ai/mcp sent initialize result auth-required (HTTP 401) 713 ms
20:04:26Z https://mcp.sendmux.ai/mcp sent initialize result auth-required (HTTP 401) 618 ms

Authentication

Auth type	OAuth with client registration
What the challenge said	`Bearer resource_metadata="https://mcp.sendmux.ai/.well-known/oauth-protected-resource/mcp", scope="analytics.read billing.read domain.create domain.read domain.verify email.send logs.read mailbox.admin.create mailbox.admin.manage mailbox.admin.read mailbox.read mailbox.settings.update webhook.create webhook.manage webhook.read"`
Protected resource metadata	mcp.sendmux.ai
Authorization server metadata	app.sendmux.ai
Registration endpoint	`https://app.sendmux.ai/oauth/register`
Client ID metadata documents	supported

The sign-in route, step by step

Request https://mcp.sendmux.ai/mcp without a token. It answers 401 and a WWW-Authenticate header.
Read the protected resource metadata at https://mcp.sendmux.ai/.well-known/oauth-protected-resource/mcp to find the authorization server.
Register a client at the registration endpoint https://app.sendmux.ai/oauth/register (dynamic client registration), so no human has to create an app first.
Send a person through the authorization page, then retry the endpoint with the bearer token. The connector stops after step 2 and never authorizes.

See OAuth for MCP: client ID metadata documents and dynamic registration for how each route works.

CLI

No CLI is on record for Sendmux. The directory checks a package only where a source names one, so this is a floor: a company can ship a command line that no source read for this edition mentions. See shipping a CLI agents can use.

Other agent surfaces

Agent surfaces other than MCP and CLI
Surface	Result
OpenAPI file	No OpenAPI file at the root paths checked.
WebMCP in the initial HTML	Not checked: the home page was not read by the shared crawl.
MCP discovery file	Not checked: the domain is not in the shared crawl for this edition.
A2A agent card	Not checked: the domain is not in the shared crawl for this edition.
A2A agent card (older path)	Not checked: the domain is not in the shared crawl for this edition.
agents.json	Not checked: the domain is not in the shared crawl for this edition.
OAuth authorization server metadata	Not checked: the domain is not in the shared crawl for this edition.
NLWeb endpoint	Not checked in this edition.

Registry listings

Registry listings
Registry	Listed
Official MCP Registry	No
GitHub MCP Registry	Yes
awesome-remote-mcp-servers	No
Smithery	Not checked: Smithery's listing pages and search API were unavailable on 4 November 2026.
Glama	Not checked: Glama's API needs a key and attribution terms.