6,622 tools, each one opened, scored and signed by a Toolio reviewer

SendMux

Give your AI agent a real inbox, not just an email wrapper.

Checked 4 Oct 2026 Reviewed by Alex Listed since July 2026

Screenshot of SendMux

At a glance

Starts at Free to start Price as published by the vendor, September 2026.
Free tier Yes, limited
Platforms Web, API
Best for AI agents and chatbots that need inboxes.
Not for Small businesses with custom SMTP needs

4.0 out of 5

Scored by Alex after real use

Our verdict

SendMux provides actual inboxes for AI agents but can be limited with provider quotas. Great for those who need full control over emails, but might struggle without more complex setups.

✓What it does well

Actual InboxesAI agents get real email inboxes with all the features of a traditional inbox.
Flexible Usage PricingPricing scales based on actual usage of email and storage.
Granular Delivery ControlSupports weighted delivery, quotas, and failover mechanisms for reliability.

✕Where it falls short

Limited Provider FlexibilityStays within supported providers, no custom SMTP setup possible.
Complex SetupSetting up and managing multiple inboxes can be cumbersome without automation tools.
Fixed Daily Limits on Free PlanFree plan has a strict limit of 50 provider-accepted recipients per UTC day.

Key features

Email Sending ToolsAPI for sending emails with various customization options.
Inbox Management APIReceive and manage incoming email events through APIs without polling.
Flexible PricingPricing based on usage rather than fixed tiers, starting free with limited features.
Server-Sent Events APIStream incoming email events without the need for polling.

Questions about SendMux

What does SendMux do?

SendMux gives AI agents real email inboxes rather than a simple email wrapper, with the features of a traditional inbox. It offers an API for sending email, an inbox management API for incoming events, and a Server-Sent Events API that streams incoming mail without polling. It runs on the web and through its API.

Is SendMux free?

SendMux is free to start, with a limited free tier. The free plan has a strict limit of 50 provider-accepted recipients per UTC day. The Pro plan costs $7 per team per month plus usage rates, and includes unlimited storage and sender credentials.

Can SendMux use a custom SMTP server?

No. SendMux stays within its supported providers, and the reviewer notes there is no way to set up custom SMTP. For that reason, small businesses with custom SMTP needs are listed among those it does not suit, while AI agents and chatbots that need inboxes are its best fit.

How does SendMux handle email delivery reliability?

SendMux offers granular delivery control, supporting weighted delivery, quotas and failover mechanisms. The reviewer counts this among its strengths, though the verdict also notes it can be limited by provider quotas. Setting up and managing many inboxes can be cumbersome without automation tools.

How does Toolio rate SendMux?

Toolio's reviewer Alex scored SendMux 4.0 out of 5 after real use. The verdict calls it a strong choice for anyone who needs full control over email for AI agents, but warns it may struggle without more complex setups. Toolio lists Wallubot, AGNT, Replai and Aigaragesale as alternatives.

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