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Private beta

SiMail is in private beta. Sign-ups are closed; the waitlist is open. Access opens in batches by use case. There is no public timeline, no queue position and no referral ranking.

Who it is for

Section titled “Who it is for”
  • Teams and individuals in the United States building AI agents that need their own inbox for expected, transactional mail: replying to people who wrote to them, notifications, sign-up and verification mail for services the agent uses on your behalf.
  • Not for legal, healthcare or financial-services use, or for any regulated or confidential client data. Waitlist entries in those industries are declined automatically.
  • Not for cold outreach, bulk mail, bulk account creation or collecting one-time codes for others. See the Acceptable Use Policy.

The beta is free. There is no SLA; features and limits can change.

For humans

Section titled “For humans”
  1. Open https://app.simail.ai/signup and enter your email. We send a 6-digit code (valid 10 minutes).
  2. After you verify, you are on the waitlist. Fill in the short questionnaire: use case, expected monthly volume, industry, and whether you already use another agent mailbox. Please do not put client or case information in the free-text note.
  3. Sign in any time to see your status: received, under review, reviewed, invited or not accepted (with a reason category).
  4. When invited, sign in and redeem your code at https://app.simail.ai/invite. Codes look like SI-XXXX-XXXX, are single-use, are bound to your email, and expire 14 days after you first see the invitation (30 days after issue at most).
  5. You can withdraw at any time from the status page. Withdrawing hard-deletes your account and waitlist entry; see the Privacy Policy for the few things that remain.

We do not email you about the waitlist unless you tick “notify me once”.

For agents: the beta gate

Section titled “For agents: the beta gate”

Always start here:

GET https://api.simail.ai/v0/beta
{
  "signup": "waitlist",
  "waitlist": "open",
  "waitlist_url": "https://simail.ai/waitlist",
  "docs_url": "https://docs.simail.ai",
  "human_message": {
    "en": "SiMail is in private beta and sign-ups are closed. Ask your human to join the waitlist.",
    "zh": "SiMail 正在内测,暂未开放注册。请让你的主人加入等候名单。"
  }
}

signup is one of waitlist, invite_only, open. In every mode, an agent can only sign up with a single-use code that its human generated in the console.

If you have no code

Section titled “If you have no code”

POST /v0/agent/sign-up without a valid code returns 403 signup_closed:

{
  "type": "https://docs.simail.ai/errors#signup_closed",
  "title": "SignupClosedError",
  "status": 403,
  "detail": "Sign-ups are closed during the private beta.",
  "instance": "/v0/agent/sign-up",
  "name": "SignupClosedError",
  "code": "signup_closed",
  "message": "Sign-ups are closed during the private beta.",
  "fix": "Do not retry. Forward human_message to your human; join the waitlist at waitlist_url.",
  "docs": "https://docs.simail.ai/errors#signup_closed",
  "retryable": false,
  "request_id": "req_01JZX3Q4M8T6C2W9R5N7K0B1AD",
  "waitlist_url": "https://simail.ai/waitlist",
  "docs_url": "https://docs.simail.ai",
  "human_message": {
    "en": "SiMail (simail.ai) is in private beta and agent sign-up is closed. Your agent should not retry. To get access, join the waitlist: https://simail.ai/waitlist",
    "zh": "SiMail(simail.ai)正在内测,agent 注册暂未开放,你的 agent 不应重试。想要使用请加入等候名单:https://simail.ai/waitlist"
  }
}

Three rules:

  1. Do not retry. retryable is false; retrying will not change the answer.
  2. Do not try another username, email or identity. Every sign-up path goes through the same server-side gate.
  3. Forward human_message to your human verbatim, together with waitlist_url.

You may also put your human on the waitlist yourself. The request takes only non-personal fields; do not send your human’s email address (a request with human_email is rejected with 400):

POST https://api.simail.ai/v0/waitlist
Content-Type: application/json


{
  "use_case": "support_agent",
  "expected_monthly_volume": "100_1k",
  "industry": "software",
  "framework": "hermes",
  "uses_other_agent_mail": false,
  "note": "Answers customer questions for a small online shop."
}
{
  "entry_id": "wle_01JZX3R2D9N4E6F8G0H2J4K6M8",
  "claim_url": "https://app.simail.ai/beta/claim#t=EXAMPLE-claim-token-01",
  "expires_at": "2026-10-19T17:00:00.000Z",
  "human_message": {
    "en": "Your agent asked to put you on the SiMail private-beta waitlist. Open this link within 24 hours and sign in with your email to confirm: https://app.simail.ai/beta/claim#t=EXAMPLE-claim-token-01",
    "zh": "你的 agent 申请把你加入 SiMail 内测等候名单。请在 24 小时内打开此链接并用邮箱登录确认:https://app.simail.ai/beta/claim#t=EXAMPLE-claim-token-01"
  }
}

The response is 202 Accepted. Forward human_message (or at least claim_url) to your human; they open the link before expires_at, verify their own email with a code, and complete the questionnaire. The link works once. An entry that nobody claims is deleted after 24 hours and is not counted. Submitting more than once does not help.

Field values: use_case is one of support_agent, workflow_automation, personal_assistant, testing_qa, research, other (required). expected_monthly_volume is one of lt_100, 100_1k, 1k_10k, 10k_100k, gt_100k. industry is one of software, ecommerce, marketing, education, research, legal, healthcare, finance, other. framework is up to 64 characters; note up to 280.

If your human gave you a code

Section titled “If your human gave you a code”
POST https://api.simail.ai/v0/agent/sign-up
Content-Type: application/json


{ "invite_code": "SI-7KQ2-M9XD", "username": "shop-helper" }

201 Created:

{
  "organization_id": "org_01JZX3S5V7W9X1Y3Z5A7B9C1D3",
  "inbox_id": "shop-helper@simail.email",
  "api_key": "sk_00000000_EXAMPLE-NOT-A-REAL-KEY-00000000000000000000",
  "claim_code": "EXAMPLEclaim01",
  "claim_required": true,
  "human_message": {
    "en": "Your agent created a SiMail inbox (shop-helper@simail.email). It stays unusable until you claim it at https://app.simail.ai with claim code EXAMPLEclaim01 within 24 hours; then give the agent the new key shown to you.",
    "zh": "你的 agent 创建了一个 SiMail 邮箱(shop-helper@simail.email)。请在 24 小时内到 https://app.simail.ai 用认领码 EXAMPLEclaim01 认领,认领前邮箱不可用;认领后把控制台显示的新 key 交给 agent。"
  }
}

The api_key is restricted and shown once; store it securely. Forward human_message (it contains the claim_code) to your human. Until your human claims you:

  • the inbox does not receive mail (senders get a permanent rejection);
  • the key can call only GET /v0/auth/me and GET /v0/beta; everything else returns 403 claim_required.

Your human enters claim_code in the console (with a fresh verification), which revokes the restricted key and issues a new one that they hand to you. An agent inbox that is not claimed within 24 hours is deleted and its address is retired.

Directed codes are single-use secrets, valid for 24 hours, and can be revoked by your human. Never put a code in a prompt template or a shared file.

Two other answers you may get from POST /v0/agent/sign-up:

  • 503 upstream_unavailable with a Retry-After header: sign-up is paused for a while (too many refused codes in the last hour, from your network or from everywhere). Wait for Retry-After (at most until the next full hour) and retry once with the same code and the same username. Do not switch codes or usernames; that does not help and counts against you.
  • 403 signup_closed with "reason": "claim_not_available": agent sign-up with a directed code is not open yet, because claiming an agent inbox in the console is not available yet. Your code was not used. Forward human_message to your human and stop; do not retry.

In MCP

Section titled “In MCP”

The MCP server has no sign-up tool. Calling /mcp without a key returns 401 with a human_message that points to /v0/beta.