## TL;DR
The agent must only send to addresses that came from a trusted source (your CRM, a form submission, an explicit list) and must never construct or guess an address. Validate every address syntactically before sending, and quarantine anything that fails. Hallucinated addresses hard-bounce, and hard bounces torch your sender reputation fast.

```text
agent hallucinated email addresses that all hard-bounced
```

## Use this when
- sends go to addresses nobody provided
- bounce rates spike after an agent run
- the agent helpfully fills in missing contact info

## Not for this skill when
- the list itself is stale (clean the list)
- you need better email copy
- bounces come from full inboxes or blocks (different problem)

## Steps
1. Define the allowed address sources (CRM export, signup form, manual list) and reject any address not traceable to one. Verify: every send row names its source.
2. Add a hard rule: the agent never generates, guesses, or completes a partial address. Verify: a test run with missing data skips the row instead of inventing one.
3. Validate syntax on every address before queueing (use a standard validator, not a regex you wrote). Verify: malformed addresses land in quarantine, not in the send queue.
4. In drafts and examples use [recipient email] as the placeholder, never a made-up address. Verify: no example address appears anywhere in templates.
5. Monitor hard-bounce rate per run; pause sending if it crosses 2 percent. Verify: the pause triggers automatically, not by someone noticing.

### Tool/version compatibility
Any email sender or CRM. Syntax validation libraries exist in every language; the source-tracing rule is process, not code.

## Why it happens
The agent is a completion engine: given a task like contact the marketing lead at Acme, it completes the pattern with a plausible-looking address. Plausible is not real, and mail servers answer with bounces.

## Edge cases / pitfalls
- Role addresses like info or support at a domain are real but often unmonitored; decide deliberately whether to send to them.
- Validated syntax is not a validated human; syntax checks catch typos, not fiction. Source tracing is the real guard.
- Never buy or scrape lists to fix coverage; that trades one reputation problem for a worse one.

## Variant phrasings
### Agent made up email addresses that bounced
Short version: hallucinated recipients.
### Sends went to guessed addresses and killed deliverability
Short version: invented addresses hard-bounced.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_9Az8Vy94yrX4cvAOJlzF7g