---
name: deliverability
description: tinysend sender domains and deliverability — DKIM/SPF/return-path DNS setup, verification, automatic warm-up, bounce and spam-complaint handling, reputation. use when configuring a custom sending domain or debugging why email doesn't arrive.
license: MIT
compatibility: requires network access to api.tinysend.com (see the platform skill for auth)
---

# deliverability

how tinysend handles email deliverability, DNS authentication, and sender reputation.

## sender domain setup

each newsletter can send from its own domain (e.g. newsletter@yourdomain.com).

setup flow:
1. PUT /v1/lists/:id/sender with { type: "custom_domain", name, email, domain } — creates the domain in Postmark, returns DNS records
2. add the returned DNS records (DKIM TXT, return-path CNAME, SPF TXT) at the domain provider
3. verification runs automatically every minute; POST /v1/lists/:id/sender/check forces an immediate re-check
4. until verified, emails keep sending from @tinysend.com — verified domains switch over automatically

### checking status

```
GET /v1/lists/:id/sender — mode, from_address, per-record found/not-found, plain-language next step
```

### removing

```
DELETE /v1/lists/:id/sender — reset to the @tinysend.com default
```

(/v1/lists/:id/domain is a deprecated alias for /sender.)

## warm-up

new sender domains go through automatic warm-up to build reputation.

stages:
- day 1-7: low volume, provider-distributed sending
- day 8-14: gradually increasing limits
- day 15+: full volume

tracked per newsletter via GET /v1/lists/:id — shows warmup status, daily limits, sent counts.

## bounce handling

tinysend automatically handles bounces:
- hard bounces: subscriber marked as undeliverable, removed from future sends
- soft bounces: retried, subscriber flagged after repeated failures
- spam complaints: subscriber immediately unsubscribed, complaint logged

related webhook events: `email.bounced`, `email.complained`

## reputation management

- isolated sending infrastructure per newsletter
- automatic warm-up for new domains
- bounce/complaint thresholds trigger alerts
- provider-aware sending (gmail, outlook, yahoo distributed separately during warm-up)