Sending

POST https://app.ruber.me/api/v1/messages

Required permission: Sending → Write (messages:send) Sending is a separate permission from everything else. messages:write lets a key file and star mail that already exists; it does not let it send. Mail sent here leaves under your domain’s reputation and spends your plan’s daily allowance, so granting it is a deliberate choice.

Request

curl -X POST https://app.ruber.me/api/v1/messages \
  -H "Authorization: Bearer rk_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "you@yourdomain.com",
    "to": ["customer@example.com"],
    "subject": "Your order has shipped",
    "text": "It is on its way — tracking is attached.",
    "html": "<p>It is on its way — tracking is attached.</p>"
  }'

const response = await fetch("https://app.ruber.me/api/v1/messages", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.RUBER_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    from: "you@yourdomain.com",
    to: ["customer@example.com"],
    subject: "Your order has shipped",
    text: "It is on its way.",
  }),
});

import os, requests

requests.post(
    "https://app.ruber.me/api/v1/messages",
    headers={"Authorization": f"Bearer {os.environ['RUBER_API_KEY']}"},
    json={
        "from": "you@yourdomain.com",
        "to": ["customer@example.com"],
        "subject": "Your order has shipped",
        "text": "It is on its way.",
    },
)

Field	Type
`from`	string	required. A mailbox or alias your organization owns.
`to`	array or string	required. Up to 25 recipients.
`cc`	array or string	Up to 25.
`bcc`	array or string	Up to 25.
`subject`	string	Up to 200 characters.
`text`	string	Plain-text body, up to 100,000 characters.
`html`	string	HTML body, up to 400,000 characters. Sanitised before sending.
`in_reply_to`	string	The `message_id` you are replying to.
`references`	array	Message IDs of the thread.
`attachments`	array	Up to 10, 8 MB total. See below.

Address fields accept either an array or a comma-separated string. Both are common in the wild and neither is wrong.

from may be a mailbox or an alias. An alias sends as itself — that is what the recipient sees — while the mailbox behind it authenticates, files the copy in its Sent folder and carries the sending limits. List them with GET /v1/aliases.The limits key on the owning mailbox, never the alias. Otherwise one mailbox could multiply its own daily allowance by inventing addresses, which a catch-all makes free.Private mailboxes cannot send through the API at all: the message would have to be encrypted with a key only the owner’s browser holds.

Attachments

Each entry is filename, base64 content, and an optional content_type (defaults to application/octet-stream).

{
  "from": "you@yourdomain.com",
  "to": ["customer@example.com"],
  "subject": "Your invoice",
  "text": "Attached.",
  "attachments": [
    {
      "filename": "invoice.pdf",
      "content_type": "application/pdf",
      "content": "JVBERi0xLjQKJcfsj6IKNSAwIG9iago8PC9..."
    }
  ]
}

At most 10 attachments totalling 8 MB decoded. The ceiling leaves headroom under SES’s ~10 MB message limit once MIME encoding is added — base64 inflates content by roughly a third, and that inflation happens after this check.

Response

202 Accepted. The message has been handed to the mail server, which is not the same as delivered — remote servers accept and bounce on their own schedule.

{
  "accepted": ["customer@example.com"],
  "rejected": [],
  "message_id": "<2f8c1e40-9d7a-4b3e-8c11-0a2f6b7d9e10@yourdomain.com>"
}

A recipient in rejected was refused by the mail server outright — usually a malformed address. Recipients in accepted were taken for delivery. A copy is filed in the Sent folder automatically. If that filing fails the send still reports success: the message has already gone, and reporting failure would invite you to send it twice.

Limits

Sending passes several ceilings, and they fail differently:

Limit	Scope	Error
600 requests/minute	per API key	`rate_limited`
50 messages/hour	per mailbox	`rate_limited`
5 messages/10 seconds	per mailbox	`rate_limited`
Plan’s daily allowance	per organization	`quota_exceeded`

The per-mailbox limits are the ones that decide whether a leaked key can burn your domain’s reputation before you notice, so an API key does not get a more generous version of them than the web app has. The daily allowance is the entitlement your plan sells, and it is shared: messages sent from the dashboard and through the API draw on the same counter. rate_limited carries a Retry-After header. quota_exceeded does not — the allowance resets at midnight UTC.

Errors

Code	HTTP	Cause
`invalid_request`	`400`	Malformed JSON, a bad address, no recipients, attachments over 8 MB, or `from` is a Private mailbox.
`unauthorized`	`401`	Missing, malformed, unknown or revoked key.
`quota_exceeded`	`402`	Your plan’s daily sends are used up.
`forbidden`	`403`	The key lacks `messages:send`.
`not_found`	`404`	`from` is not a mailbox or alias on this account.
`rate_limited`	`429`	One of the sending limits above. See `Retry-After`.
`mail_unavailable`	`502`	The mail server refused the message. Nothing was sent.

See Errors for the full response shape.

Start here

Using Ruber

API

Request

Attachments

Response

Limits

Errors

​Request

​Attachments

​Response

​Limits

​Errors

Request

Attachments

Response

Limits

Errors