# StableEmail Inbox Quarterly Top-Up

> StableEmail Inbox Quarterly Top-Up is a paid API for AI agents from stableemail.dev, paid per call via x402, $2.5/call, status unknown (last checked 2026-09-13).

Extends an existing StableEmail inbox by 90 days for $2.50 USDC (17% savings over the monthly rate)

## Facts

- Endpoint: POST https://stableemail.dev/api/inbox/topup/quarter
- Price: $2.5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/stableemail-7bc76ac8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Bop03plhoS7Bc91Ag6wTz

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability stableemail-7bc76ac8 -d '<json body>'
```

Example prompt: Top up my StableEmail inbox for 90 days — I want the quarterly plan to save a bit.

## When to prefer this

Choose this endpoint over the 30-day top-up ($1) when the inbox needs to stay active for a full quarter and cost savings matter; 90 days costs $2.50 vs $3.00 for three separate monthly renewals. Best when an agent or workflow depends on a stable inbox address over an extended period without frequent renewal calls.

## Known failure modes

- Inbox not found or invalid subdomain — returns 404 or equivalent error
- Payment failure or insufficient USDC balance — returns payment error
- Inbox already deleted or permanently expired — cannot be renewed
- Duplicate top-up attempt within a short window — may return conflict error
- Network timeout during payment processing — ambiguous state, retry needed

## How this service works

Top up inbox 90 days ($2.50, save 17%)

## Output

Returns confirmation that the inbox has been extended by 90 days, updated expiry timestamp, and current inbox status after the renewal payment of $2.50 USDC is processed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "username": {
   "type": "string",
   "allOf": [
    {
     "pattern": "^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$"
    },
    {
     "pattern": "^(?!.*--)"
    }
   ]
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stableemail-7bc76ac8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stableemail.dev](https://www.zero.xyz/host/stableemail.dev/llms.txt)