How it works

From upload or API call to the mailbox.

Rush Mail runs the same pipeline whether you upload a single letter in the dashboard or send a million through the API. Here is what happens after you hit send.

Connect

Create an account and grab an API key. Use the dashboard for one-off sends or the API for everything programmatic. No vendor onboarding per state.

Send

POST your PDF and recipient address to /v1/letters, or upload a document in the dashboard. Set certified=true when you need proof of delivery.

We produce & mail

We validate the address, print, fold, insert, and hand the piece to USPS — produced and inducted within one business day of the daily cutoff.

Track

Subscribe to webhooks or poll the API for real-time status. Certified pieces return an electronic return receipt and timestamped delivery history.

The send pipeline

  1. POST /v1/letters
    Submit document + recipient
  2. Validation
    CASS address check + standardization
  3. Production
    Print, fold, insert
  4. Induction
    Handed to USPS
  5. Tracking
    Status webhooks fire
  6. Delivered + proof
    Return receipt on certified

Letters submitted before the daily cutoff are produced and inducted the next business day.

Status webhooks

Every status change, pushed to you.

Subscribe once and Rush Mail posts a callback at each stage of the lifecycle. Build your own audit trail without polling.

  • letter.createdAccepted and queued for production.
  • letter.mailedInducted into the USPS mailstream.
  • letter.in_transitMoving through the USPS network.
  • letter.deliveredDelivered; proof available on certified.
  • letter.returnedReturned to sender as undeliverable.
webhook payload
{
  "event": "letter.delivered",
  "data": {
    "id": "ltr_8f2a1c",
    "certified": true,
    "tracking_number": "9407...",
    "status": "delivered",
    "delivered_at": "2026-01-14T16:32:00Z"
  }
}

Replace the mailroom. Keep the paper trail.

Start sendingRead the docs