# Core concepts

> How outbound actually works — deliverability, sender reputation, sequencing, and AI SDRs explained as mechanisms, independent of any product.

**This section explains the machinery underneath outbound — how mailbox providers score senders, why warm-up exists, what SPF, DKIM, and DMARC actually verify, how sequence cadence affects results, and what an AI SDR really automates. Every page is written to be true even without Reply, then links to how Reply implements it.**

_Status: Reviewed — human-edited, facts not yet confirmed against the product._

These pages explain **mechanisms, not features**. Each one answers a "how does X actually
work" question in product-neutral terms first, and only then links to the Reply
implementation. If you want product behavior directly, go to
[Capabilities](/capabilities) or [Behavior](/behavior).

## Deliverability mechanics

- [Email deliverability](/learn/email-deliverability) — What decides whether a message lands in the inbox, spam, or nowhere
- [Sender reputation](/learn/sender-reputation) — The score mailbox providers keep on every sending identity
- [Email warm-up](/learn/email-warm-up) — Why new mailboxes must earn volume gradually
- [SPF, DKIM, DMARC](/learn/spf-dkim-dmarc) — What the three authentication records actually verify

## Outreach and AI

- [Sequence design](/learn/sequence-design) — Cadence theory: steps, spacing, and channels that get answers
- [Multichannel strategy](/learn/multichannel-strategy) — Why channels compound instead of just adding up
- [The AI SDR model](/learn/ai-sdr-model) — Autonomy levels, what AI actually automates, and honest limits
- [Reply classification](/learn/reply-classification) — How incoming replies are sorted into intents, and why it is hard

## How these pages are written

Every explainer follows the same shape: what the mechanism is, why it works that way, how
it behaves in practice, common misconceptions, how Reply implements it, and where the
mechanism itself breaks down. The product enters only in the second half — the first half
stays true even if you never use Reply.

## Related

- [Capabilities](/capabilities) — can Reply do X?
- [Behavior](/behavior) — the deterministic product logic
- [Playbooks](/playbooks) — applied recipes for specific situations