Sendmux: Email and calendar API built specifically for AI agents

What it is

Sendmux is an email and communication API built specifically to give autonomous workers and automated assistants dedicated inboxes and message routing capabilities. Traditional mail systems return large blocks of HTML that waste token compute limits. This product converts raw messages into structured JSON formats, stripping signatures and quoted history by default so automated models process only relevant text.

Key features

Agent-shaped inboxes delivering clean JSON payloads instead of raw HTML
Outbound email sending via HTTP or SMTP without vendor lock-in
Provider routing with automatic failover, delivery groups, and multi-level quotas
Real-time updates using server-sent events, signed webhooks, and typed change polling
Multi-tenant team support with isolated workspaces and scoped API keys

Who it's for

Sendmux targets developers, development teams, and enterprise builders creating automated customer support, sales outreach, scheduling, and monitoring workflows powered by language models.

Pricing

Sendmux offers a Free tier with fixed limits and a $1 usage credit. The Pro plan costs $7 per team monthly plus metered usage based on actual events such as connected outbound recipients, managed sending, inbound deliveries, and storage.