Promote Sign in Sign up

Email 2026 Rank: #2561

Sendmux ✓

Email API built for AI agents.

462 views 3 saves Paid
Agent AI Email API API
More categories (4)
One-Platform Solution Provider Routing Flexibility Routing Control Email
Visit website Sign in to save

from $0.15

Privacy Terms

Verdict

A quick read before you dig into the full page.

Best if
Email API built for AI agents
Skip if
Complex setup process
Pick this when
Agent-shaped mailboxes

Considering hi ai instead? Compare side by side

Overview

Sendmux is an Email API primarily designed to cater for AI agents, offering features such as agent inboxes, outbound routing via user-designated providers and automatic failover.

It provides a unified API surface that simplifies tasks related to outbound mails, agent mailboxes, routing control and delivery events. One of its key features allows users to create agent-shaped mailboxes either on verified domains or shared agent-specific domains.

The API ensures that raw message contents are available upon request and facilitates tasks like stripping signatures and quoted history, optionally making links, headers, and attachments available.For outbound emails, Sendmux allows users to break free from provider lock-ins, enabling sending from a mailbox over HTTP or SMTP protocols.

It also ensures safe HTTP retries through Idempotency-Key support. The platform also incorporates messaging routing considerations, allowing users to bind a mailbox key to all active providers, selected providers or delivery groups and implement control measures such as provider weights and quotas to manage traffic.Sendmux also eradicates the need for polling loops through use of signed webhooks for server delivery, an SSE stream for real-time mailbox clients, and typed change polling when a client needs to resync its state.Ultimately, Sendmux offers a one-platform solution, helping you coordinate services that were previously disjointed, ensuring the AI agents focus on the content rather than parsing formatting.

It also provides provisions for flexibility, enabling you to bring your own providers or route across multiple accounts.

Sendmux website

Access & connections

Where you can use Sendmux, and what it plugs into.

Platforms

Web

Integrations

Webhooks MCP

API

Public API available

Browse other tools with an API

Capabilities

What this tool accepts, produces, and is strongest at.

Input

  • API

Output

  • API

Highlights

  • API
  • MCP
  • Agents

Supported features

  • Email
  • API
  • MCP
  • Agents
  • Automation
  • Integrations
  • Docs

Pros & cons

Pros

  • Agent-shaped mailboxes
  • Unified API surface
  • Outbound routing flexibility
  • Automatic failover
  • Raw message content access
  • Strip signatures and quoted history
  • HTTP or SMTP protocols support
  • Idempotency-Key for HTTP retries
Show 18 more
  • Mailbox key binding
  • Provider weights and quotas
  • Eliminates need for polling loops
  • Signed webhooks for server delivery
  • SSE stream for real-time updates
  • Typed change polling
  • Option to bring your own providers
  • Eliminates provider lock-in
  • Covers services previously disjointed
  • Allows provider routing across multiple accounts
  • Agent inbox creation
  • Clean JSON format emails
  • Strips HTML noise from incoming mails
  • Supports mail control via API
  • Dedicated mailboxes for each agent
  • Unified inbox for all agents
  • Supports keyboard-driven view
  • Inbox search across the fleet

Cons

  • Lacks explanatory documentation
  • No multi-language support
  • Complex setup process
  • UI not user-friendly
  • No integration guidance
  • Absence of trial version
  • Cost per email sent
  • No dedicated support channel
Show 2 more
  • Absence of offline capabilities
  • No customization options

Compare alternatives

Similar tools in the catalog — with a clear reason to open each one.

Why look Higher community rating

Full comparison

Why look Freemium alternative

Full comparison

Why look Higher community rating

Full comparison

Why look Freemium alternative

Full comparison

Why look Freemium alternative

Full comparison

from $0.39/mo

Full comparison

Releases 1

Initial release June 26, 2026 Current
Initial release of Sendmux.

FAQ 12

What is Sendmux?
Sendmux is an Email API built to cater for AI agents. This platform is primarily designed to unify tasks like outbound mails, agent mailboxes, routing control, and delivery events. It allows users to create agent-shaped mailboxes on verified domains or shared agent-specific domains. It also enables users to free themselves from provider lock-ins by allowing the use of mailbox over HTTP or SMTP protocols to send mails.
How does Sendmux work?
Sendmux works by offering a unified API surface that simplifies tasks related to outbound mails, agent mailboxes, routing control, and delivery events. It allows users to create agent-shaped mailboxes, which can be created on verified domains or shared agent-specific domains. Sendmux supports both HTTP and SMTP protocols for outbound emails and allows users to break free from provider lock-ins. It ensures safe HTTP retries through Idempotency-Key support. Sendmux also continuously updates its user's status through server delivery using signed webhooks, an SSE stream, and typed change polling.
What is the key feature of Sendmux?
A key feature of Sendmux is its ability to create agent-shaped mailboxes on either verified domains or shared agent-specific domains. It provides a unified API surface that simplifies tasks related to outbound mails, agent mailboxes, routing control, and delivery events. Furthermore, Sendmux not only ensures that the raw message contents are available upon request but also facilitates tasks like stripping signatures and quoted history, optionally making links, headers, and attachments available.
How does Sendmux handle outbound emails?
For outbound emails, Sendmux enables users to break free from provider lock-ins, enabling sending from a mailbox over HTTP or SMTP protocols. With its Idempotency-Key support, Sendmux ensures safe HTTP retries. It incorporates considerations into the messaging routing, allowing users to bind a mailbox key to all active providers, selected providers, or delivery groups, thereby implementing control measures such as provider weights and quotas to manage traffic.
How are agent-shaped mailboxes created in Sendmux?
In Sendmux, users can create agent-shaped mailboxes on either verified domains or shared agent-specific domains. Users have the flexibility to customize their domains to better manage and segregate their emails tailored to their respective needs.
Does Sendmux allow raw message contents to be available upon request?
Yes, Sendmux ensures that raw message contents are made available upon request. This feature enhances the user's control over how they receive and manage their emails, ensuring that no crucial information is overlooked or lost in the process.
What tasks does Sendmux facilitate in relation to emails?
Sendmux facilitates a multitude of tasks related to emails. Aside from making raw message contents available upon request, it aids in tasks like stripping signatures and quoted history. It also has the capability to make links, headers, and attachments available, increasing the adaptability and relevance of sent messages according to the users' preferences.
What are the routing considerations Sendmux incorporates for messaging?
Sendmux incorporates several routing considerations into its messaging structure. It allows users to bind a mailbox key to all active providers, selected providers, or delivery groups. Further, it lets users implement controls like provider weights and quotas to effectively manage traffic.
How does Sendmux eradicate the need for polling loops?
Sendmux eradicates the need for polling loops by utilizing signed webhooks for server delivery, an SSE stream for real-time mailbox clients, and typed change polling for clients that need to resynchronise their state. These features work together to provide a seamless experience where continuous polling loops are now a thing of the past.
Can Sendmux allow me to bring my own email providers?
Yes, Sendmux enables you to bring in your own email providers. It provides the users with the flexibility to choose their preferred providers, promoting greater control over how they send their emails and manage their communications.
What flexibility does Sendmux offer in terms of provider routing?
Sendmux offers substantial flexibility in terms of provider routing. The system allows users to break free from provider lock-ins and send from a mailbox over either HTTP or SMTP protocols. It also gives users the freedom to bring their own providers or route across multiple accounts, ensuring adaptability and customization in accordance with their personal or business communication requirements.
How does Sendmux's Idempotency-Key support ensure safe HTTP retries?
Sendmux employs Idempotency-Key support to ensure safe HTTP retries. This feature ensures that commands meant to be executed only once do not inadvertently get executed multiple times due to network issues. This supports the reliability and accuracy of Sendmux's email services.
Sendmux from $0.15
Visit website