```meta
title: Lição com autoteste
description: A short lesson, a self-test with multiple-choice questions and a score, and a form that keeps each learner's answers with their account. Without the answers collection the form offers its @schema (collection answers, accepts anyone: lesson text, answer long_text) to whoever cares for the space, created with one click.
```

:::section width:normal space:4
## Lesson 1: how mail finds its way

Three DNS records decide whether a message arrives. **MX** says where the domain's mail is delivered, **SPF** lists the servers that may send for it, and **DKIM** signs each message so the receiver can tell it was not changed on the way.

### Check yourself

Pick an answer for each question. Your score stays in this browser; try again starts over.

```@flashcards label:"Self-test"
Which record says where a domain's mail is delivered? | MX :: The mail exchanger: where mail for the domain goes. | SPF :: SPF lists who may send, not where mail arrives. | DKIM
Which record lists the servers that may send for the domain? | SPF | MX :: MX is where mail arrives, not who sends it. | DKIM :: DKIM signs messages; it names no servers.
What does DKIM add to each message? | A signature | An address to reply to | A delivery receipt
```

### Your answer

Sign in and write what you would check first when mail goes missing. It is kept with your account, so you find it on any device.

```@form collection:answers scope:viewer submit:"Save my answer"
lesson
answer long_text
```
:::