Junior is an AI employee that lives in Slack, Teams, Lark, and email. Each one needed a real email identity for actual two-way conversations, not transactional notifications. Building that in-house meant weeks of email-infrastructure work. AgentMail made email a first-class channel in under a week.
Company: Junior, an AI employee that businesses hire as an AI coworker, built by Kuse Inc.
Problem: Give every AI employee a real email identity for two-way conversations, and provision hundreds of inboxes programmatically, without building an email platform from scratch
Result: Email went from "not a supported channel" to a first-class platform in under a week. Inbox provisioning takes ~200ms via API, the entire email gateway is ~1,200 lines of Python, duplicate deliveries are zero, and email-only teams can now run Junior fully headless.
Stack: AgentMail + Junior
What Junior Is
Junior is an AI employee. Businesses hire an AI coworker that lives in Slack, Teams, Lark, or email, connects to 3,000+ tools, and runs sales, marketing, and ops alongside the human team. It shows up as a teammate, takes initiative, and reports back with finished work instead of waiting to be prompted.
Email is one of Junior's core interaction channels. Each AI employee gets its own inbox, like sales-assistant@junior-mail.com, so customers can email their Junior directly and get real, contextual replies. Not canned autoresponders, but actual work: drafting follow-ups, pulling CRM data, scheduling meetings. For that to work, the inbox can't be a notification relay. It has to be a real, two-way mailbox the AI employee owns.
The Problem
Junior needed to give every AI employee a real email identity on the internet, one that could hold actual two-way conversations, not just send transactional notifications.
The team initially planned to build their own email infrastructure, then quickly saw how much complexity that involves: MX records, deliverability, spam prevention, proper email headers, threading logic, attachment handling, bounce management. Traditional providers didn't solve it either. Gmail requires per-user accounts with OAuth and phone verification. Outlook needs Workspace seats. Both have abuse-detection systems that flag automated usage. None of that survives spinning up hundreds of inboxes programmatically with reliable two-way email.
So the requirement was sharp: hundreds of inboxes on demand, real send and receive, no email platform to build and maintain.
Why AgentMail
AgentMail was the only API built around the inbox as the primitive.
"AgentMail was the only API built around the inbox as the primitive. Every other option was either send-only (Resend, SendGrid) or required connecting to an existing human mailbox (Nylas, Gmail API). AgentMail let us call
client.inboxes.create()and have a working inbox in milliseconds, no domain verification wait, no OAuth dance, no manual setup. The webhook pipeline (Svix-signed, at-least-once delivery) plugged directly into our gateway. We went from 'email isn't a supported channel' to 'email is a first-class platform' in under a week."Austin Xu, Co-founder and CTO, Junior
Every other option was either send-only or required connecting to an existing human mailbox. AgentMail's model fit Junior's exactly: one API call creates a real inbox in milliseconds, and a signed webhook pipeline delivers inbound events straight into Junior's gateway.
On implementation, the integration was fast.
"The Python SDK is clean, the docs have code examples for every endpoint, and the webhook format is straightforward. We built our entire email gateway, doing inbound signature verification, sender policy enforcement, dedup, dispatch to the AI runtime, and outbound replies, in about 1,200 lines of Python. The team has been very responsive on issues and feedback. When we ran into edge cases or had feature requests, we got quick replies and fixes. It's clear they care about the developer experience."
Austin Xu, Co-founder and CTO, Junior
The Numbers
| Before | After | |
|---|---|---|
| Email infrastructure | Planned to build from scratch: MX, deliverability, spam, threading, bounce handling | Integrated AgentMail in under a week; "it basically just works" |
| Email as a channel | Not a supported channel | A full platform: inbound and outbound, threading, attachments, sender policies |
| Inbox provisioning | N/A | ~200ms via API |
| Duplicate deliveries | A risk to handle | Zero, thanks to webhook dedup |
| Email-only teams | Required a chat app | Can run Junior entirely headless, no chat app required |
Virtually no issues since launch.
"AgentMail is the first one built purely for AI agents. It's a great inbox."
Austin Xu, Co-founder and CTO, Junior
Products used: Programmatic inboxes, Send and Receive, Threaded conversations, Drafts, Labels and automatic labelling, Attachments, Webhooks, IMAP and SMTP, Custom domains.
Building something similar? console.agentmail.to/sign-up
AgentMail gives your agents real inboxes. Create inboxes via API. Send and receive Emails with 0 complexity. Free to start.
