Sendmux
Verified Oct 15, 2026 ActiveEmail API for AI agents: real inboxes, sending through your own providers with failover, and inbound events over one API.
Listed on EffectHub ·
Pricing
- Pricing model
- Freemium
- Paid options from
- $7/mo
- Billing
- Monthly
Free plan has fixed limits (one domain, two mailboxes, a $1 usage credit, a 'sent via Sendmux' footer). Pro is $7 per team/month plus prepaid usage: $0.50 per 1,000 accepted recipients through your own providers, $0.75 per 1,000 through the managed account, $0.50 per 1,000 inbound deliveries and $0.02 per GB-month of storage; Enterprise is custom.
Use tool ↗About Sendmux
Sendmux gives AI agents their own mailboxes and a single API to send, receive and react to email, with calendar and file storage now added alongside. Outbound mail can go through your own Gmail, SendGrid, Mailgun, Resend or SMTP accounts with weighted routing, quotas and automatic failover, or through a built-in managed account. Inbound mail arrives as events over server-sent streams or webhooks, with bodies cleaned up so an LLM does not spend tokens on raw HTML. It ships TypeScript and Python SDKs, a CLI, a hosted MCP server and agent skills, and is run by an Australian company from Melbourne.
- Platforms
- Web · API
- API
- Yes
- Last verified
- Oct 15, 2026
Verified sources
- Pricing page: Free $0 per team with fixed limits and a $1 usage credit; Pro $7 per team/month plus usage at $0.50 per 1,000 connected outbound recipients, $0.75 per 1,000 managed, $0.50 per 1,000 inbound deliveries and $0.02 per GB-month; Enterprise custom (15 October 2026)sendmux.ai ↗
- Terms of Service (updated 25 May 2026) are with Jonah and Associates Pty Ltd, operating as Sendmux, registered in Victoria, Australia; footer reads Made in Melbourne (15 October 2026)sendmux.ai ↗
- Home page describes mailboxes, calendars and files through one API, sending via Gmail, SendGrid, Mailgun, Resend or SMTP with failover, SDKs, CLI and a hosted MCP endpoint (15 October 2026)sendmux.ai ↗
- Privacy policy effective date is 7 April 2026 (15 October 2026)sendmux.ai ↗
Is Sendmux legit?
We don’t label tools safe or unsafe. Below are the records we checked ourselves, each with the date we read it.
- Domain registered
- Feb 16, 2026Registry record (RDAP), registrar Cloudflare, Inc, looked up Sep 14, 2026
- TLS certificate
- Issued by Google Trust Services, valid until Jan 12, 2027Seen in our own connection to the site on Oct 15, 2026
- Last checked
- Oct 15, 2026The site answered
- On the market since
- 2026The vendor's own material, read by us
- Operated by
- Jonah and Associates Pty Ltd, AustraliaOur research, card verified Oct 15, 2026
Pros & cons of Sendmux
Solves a specific problem well: giving an agent an address it can send from and receive at, with event streams instead of an IMAP polling hack, and failover across the mail providers you already pay for. Pricing has moved from pure usage to a $7 team fee plus per-message rates roughly three times the earlier ones, so model your volume before assuming it is the cheap option.
Pros
- Sending, receiving, routing and inbound events behind a single API
- Weighted routing and automatic failover across Gmail, SendGrid, Mailgun, Resend and SMTP
- No seat or per-mailbox fees, and rejected recipients are not charged
- SDKs, a CLI, a hosted MCP server and agent skills for integration
- Named Australian operator with published terms, privacy policy and DPA
Cons
- Per-message rates ($0.50 per 1,000 own-provider, $0.75 managed) sit on top of whatever your own provider charges
- Free plan adds a 'sent via Sendmux' footer and allows only two mailboxes
- Pro capacity is 'unlimited' only under fair use, with increases needing admin approval
- Not a marketing-email product: no campaign or list management
Best for
- Agents that need their own inbox and reply thread
- SaaS backends wanting one API across several outbound mail providers
- Teams that refuse per-seat or per-mailbox pricing
Not for
- Marketing newsletters needing campaign and list tooling
- High-volume senders comparing raw per-message cost, where a direct provider account is cheaper
Watch out: Each accepted To, CC and BCC recipient is billed separately, and connected-provider sends are billed by Sendmux on top of your provider's own fees. Deliverability still depends on the provider behind the route and your domain authentication.