Inkbox, which emerged from Y Combinator's summer 2026 batch, has built what it calls an identity layer for autonomous software: each AI agent gets a dedicated email address, phone number, iMessage capability, and a public web endpoint bundled under a single handle.
The San Francisco startup is betting that as companies spin up dozens or hundreds of AI agents, those programs will need persistent identities to communicate with one another, with humans, and with external services. Right now that coordination tends to happen through ad hoc wiring and shared credentials. Inkbox's approach treats each agent as a first-class entity with its own mailbox, SMS line, voice channel, stable hostname, and an encrypted vault for API keys and authentication tokens.
"We didn't need another email or voice API," Ray Liao, the company's CEO, wrote when Inkbox launched publicly. "We needed one service to tie its identity together with rich context. So we built it."
Handles, mailboxes, and tunnels
The product centers on globally unique handles — something like @sales-agent — that anchor an agent's communication stack. By default, each handle owns one email inbox and one public tunnel, a stable URL such as my-agent.inkboxwire.com that routes inbound HTTP, WebSocket, or raw TCP traffic to wherever the agent is running. Teams can attach a phone number to the identity, opt into iMessage, and grant the agent access to specific secrets stored in the vault.
Email works over standard IMAP and SMTP, plus a proprietary API for programmatic sending, forwarding, and attachment handling. Agents on the Startup tier can send to as many as 5,000 recipients daily, according to Inkbox's documentation.
Phone functionality includes outbound and inbound calls with real-time audio delivered via WebSocket, plus SMS and MMS with 10DLC carrier compliance and automatic opt-out management. The company has also rolled out a beta feature it calls Voice AI, which handles phone calls end-to-end without requiring a separate server — the agent receives speech-to-text transcripts and sends text-to-speech responses directly through Inkbox's infrastructure.
iMessage support runs on a shared-router model at the lower pricing tiers: a human texts "connect @handle" to start a conversation with an agent. Paid plans offer dedicated lines that let agents initiate iMessage threads outbound.
Agent-to-agent discovery
Beyond communication primitives, Inkbox introduced what it calls the Agent2Agent protocol, or A2A. Each agent identity publishes a JSON "Agent Card" at a discoverable URL, listing authentication methods and capabilities. Other agents can query those cards, check contact policies, and open channels without manual configuration.
Agents can self-register using a six-digit human verification code. Until verified, an agent's outbound messaging is capped at five recipients per 24 hours — a spam-control measure. Single-use invitation bundles let teams connect up to 25 agents at once, bypassing individual allow-list rules.
The company runs a publicly listed support agent at the handle @support as a demonstration. Any A2A-enabled agent with permissive egress policies can open a support ticket by messaging that address.
Pricing starts free, scales to enterprise
Inkbox offers three identities free, each with email, a public URL, shared iMessage, and A2A discovery. A $30-per-month Developer plan raises the cap to ten identities, adds one phone-enabled agent with 300 SMS or MMS messages and 30 minutes of voice, and supports up to ten custom email domains. The $200-per-month Startup plan accommodates 100 identities, nine phone-enabled agents, and one dedicated iMessage line. Overage runs three cents per text message and three cents per call minute.
The startup has published plugins for ChatGPT, Claude, Cursor, and several other agent frameworks, including Hermes Agent. The Hermes integration routes mailbox, phone, and iMessage events to an agent-controlled Inkbox tunnel and hooks into OpenAI's Realtime API for voice calls, according to the open-source repository.
Early use cases
Vendo, a company referenced in an Inkbox blog post, operates five agents on Inkbox identities: engineering, go-to-market, operations, and two founder assistants. Each handles email, phone, and iMessage under its own handle, with shared context stored in the credential vault and org-level contact directories, the company said.
Inkbox also showcased the platform at MIT's Imagination in Action event earlier this year, according to a LinkedIn post from the company.
The team and competitive landscape
Liao holds a PhD in computer science from MIT and previously cofounded Empallo, where he served as CTO. Alex Wilcox, Inkbox's CTO, has a master's in computer science from Northeastern and experience in machine-learning engineering. Dima Vremenko, listed as chief AI officer, was a research associate at Harvard Medical School working on ML pipelines for electronic health records and pathology data.
The company participated in Y Combinator but has not publicly disclosed the size of its funding round. Crunchbase lists the headcount between one and ten employees, though that figure may be outdated.
Several competitors have carved out pieces of the agent-identity puzzle. Agent's Inbox, AgenticMail, and Mailtrap Agent Inbox offer email-only services. Dial provides phone, messaging, and hosted AI voice — including WhatsApp and agent-initiated iMessage on dedicated numbers — but does not bundle email, public tunnels, or a credential vault, according to a comparison chart on Dial's site. Miss Blue sells standalone iMessage API access.
Inkbox's pitch is that fragmentation across those services creates friction. The company is positioning itself toward AI engineers building multi-agent systems and startups deploying fleets of autonomous agents that need stable, discoverable identities across communication channels. Whether that bundled approach finds traction will depend on how quickly those multi-agent architectures move from prototype to production, and whether developers prefer stitching together specialized APIs or paying for an integrated stack.
