"Email tool for AI agents" is a phrase now used for two genuinely different products, and searching for one usually surfaces the other. Pick the wrong category and you'll either overpay for infrastructure you don't need, or hit a wall when the thing you bought can't do what you actually needed it to do. This page draws the line clearly, then rounds up the actual tools on each side of it — including where OTPBox fits and where it doesn't.
Problem one: an agent needs an email address the way a person has one — something it can send from, receive ongoing mail to, and use as a standing identity across sessions over weeks or months. That's infrastructure for an agent acting as a correspondent: following up on threads, maintaining a relationship with a service over time.
Problem two: a test, or an agent driving a test, needs to receive exactly one email — a signup confirmation, a one-time password, a magic link — read a code or link out of it, and throw the inbox away. No ongoing identity, no sending, usually no session longer than a few minutes. This is the shape of problem OTPBox, and a handful of adjacent tools, solve.
These aren't two tiers of the same thing; they're different infrastructure with different pricing shapes and integration points. The rest of this page treats them separately.
These give an agent a real, persistent email identity it can send from and receive to indefinitely, usually as part of a broader "let an agent act on my behalf" platform.
What both have in common: the mailbox is meant to last, the agent is expected to send as well as receive, and billing tends to track active mailboxes or messages over time rather than a handful of API calls in a CI run.
These solve a narrower, cheaper problem: hand out a throwaway address, catch whatever single message a signup or login flow sends to it, and get the code or link back out programmatically — usually as one step buried inside a larger test or agent task.
/mcp exposing 13 tools (create_test_inbox, wait_for_email, get_otp, get_verification_link, and more — see the docs), a TypeScript SDK (otpbox-sdk), and automatic OTP-code and verification-link extraction on every message, so a test reads a field instead of parsing a raw body. Free tier is 200 requests/month, no card; Pro is $9/month for 5,000 requests/month pooled across an organization's keys. It doesn't send mail or hold identity across sessions — every inbox is disposable by design, expiring an hour after creation by default.What these share: no sending, no persistent identity, and pricing that tracks API calls or messages caught rather than mailboxes maintained — because the inbox is disposable, the cost should be too.
Three questions do most of the work:
"Just catch one code," "fresh per run" and "per-call" points you at the second category — the one OTPBox is built for. See also our dedicated guide to OTP testing for AI agents with MCP.
| Tool | Category | Typical use case |
|---|---|---|
| AgentMail | Agent-owned mailbox | An agent sends and receives ongoing mail under its own persistent address |
| Nylas — Agent Accounts | Agent-owned mailbox (+ calendar/contacts) | An agent gets a managed account inside a broader communications platform |
| OTPBox | Disposable inbox for one message | A test or agent catches one signup/OTP/verification email via REST or MCP, then discards the inbox |
| temp-mail.io MCP server | Disposable inbox for one message | Same shape as OTPBox, via temp-mail.io's own MCP server |
| Community TempMail MCP servers | Disposable inbox for one message | Varies — small/community-maintained wrappers around a temp-mail API |
| Mailosaur / MailSlurp | Test-email (and SMS) platform, increasingly also agent-facing | Broad QA test automation across email (and SMS for Mailosaur), can also serve the one-off verification-email case |
OTPBox is the disposable-inbox tool, not the agent-mailbox tool — we'd rather say that plainly than blur the line to look broader than we are. If your agent needs to hold an ongoing correspondence, look at AgentMail or Nylas Agent Accounts instead. If your agent (or CI suite) just needs to sign up for something and read back a code or a link, that's the narrower problem, and it's the only one we built for: a REST API and an MCP server with 13 tools purpose-built for exactly this loop, automatic code and link extraction so nothing needs a regex, a real free tier with no card, and pooled team pricing on Pro that matches how a CI key, a staging key and a developer's local key are actually used together.
The fastest way to judge fit is to try it against your own flow: mint a free key with no account (POST /api/v1/keys/free, see the docs), or wire it into an existing suite with the Playwright or Cypress guide.
Ready to see it against your own signup flow? Create a free account
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