# How to Find Work Emails With Claude (and Verify Them)

> Find work emails with Claude: connect an email finder over MCP, verify every address, and know what valid, catch-all and unknown mean before you send.

Source: https://layrcake.dev/guides/find-work-emails-with-claude · By the Layrcake team · Published 2026-10-18 · Updated 2026-10-18

**The short answer.** To find work emails with Claude, connect an email-finding tool over MCP, give Claude names with a company website or LinkedIn profile, and have it verify every address before you use it. Across two of our runs, the finder returned 24 addresses for 28 people. The second check kept 22 as sendable, flagged 6 of those as catch-all, and caught 2 to drop.

## Can Claude find email addresses?

Not on its own. Claude, Anthropic's AI assistant, answers from training data with a cutoff date, and Anthropic's own docs describe web search as the way it reaches "real-time web content ... beyond its knowledge cutoff" ([Anthropic](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool)). Work email addresses are rarely published on the open web. So Claude needs a tool built for the job: an email finder connected over MCP (Model Context Protocol).

With one connected, the job becomes a sentence. Claude takes each person, calls the finder, then checks every address it got back. You get a list you can send to and a clear note on anything risky.

**A prompt that works**

```
Find the work email for each of these people, then verify every address. Drop anything invalid, tell me which ones are catch-all, and don't guess addresses. Budget 60 credits.
- [Name], [company website]
- [Name], [LinkedIn profile URL]
- … (one line per person)
```

## What does Claude need to find a work email?

A name and something that pins down the company: the company's website, or the person's LinkedIn profile. An email address, if you have an old one, also works as a starting point. In Layrcake, that is the `enrich` tool, and it accepts any of the three.

Ask for the email only, unless you need a phone number too. Finding emails is the expensive part of most prospecting runs, so ask for what you will use. In our runs a found email cost 5 credits, and a person with no email found cost nothing.

**Tool calls · one person**

1. `enrich` · name + company website · want: work_email → address + label · 5 cr on a hit, free on a miss
1. `verify_email` · the address enrich returned → valid · catch_all_valid · invalid · unknown … · 1.25 cr

## How many emails did Claude find?

In two runs on real lists, the finder returned an address for 24 of 28 people. The second check then disagreed with the finder more often than you might expect.

|   | Run 1 · heads of sales, London | Run 2 · heads of marketing, UK |
| --- | --- | --- |
| People | 20 | 8 |
| Address found | 16 | 8 |
| Valid on the second check | 10 | 6 |
| Catch-all | 5 | 1 |
| Invalid | 1 | 0 |
| Unknown | 0 | 1 (free) |
| Sendable | 15 | 7 |

*Run 1: 1 October 2026. Run 2: 12 October 2026. Both in Claude, both stopped before sending.*

In run 1 the finder had labelled all 16 addresses valid. The second check found one invalid and five catch-all. In both runs, one address came back on a different domain from the company the search listed. That usually means the person has moved jobs or the company has rebranded. In run 2 that address was also the one the check couldn't confirm, so it was dropped.

## Why verify an email the finder already checked?

Because a finder's label reflects what it knew when it found the address, and mailboxes change. A second check at the moment you plan to send is cheap, and a bounce is not.

The mailbox providers say so in their own sender guidance. Yahoo's tells senders to "Remove invalid recipients from your list promptly" ([Yahoo](https://senders.yahooinc.com/best-practices/)). Microsoft's, for senders of 5,000 or more messages a day to Outlook, says "Remove invalid addresses regularly to reduce spam complaints, bounces, and wasted messages" ([Microsoft](https://techcommunity.microsoft.com/blog/outlook/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730)). Google's tells bulk senders to "Automatically unsubscribe recipients who have multiple bounced messages" ([Google](https://support.google.com/a/answer/81126?hl=en)). None of the three publishes a bounce-rate threshold, so be wary of anyone quoting one as theirs.

## What do valid, catch-all and unknown mean?

A verifier asks the company's mail server whether it would accept mail for the address, without sending anything. The answer comes back as one of a few statuses. These are the ones Layrcake's `verify_email` returns, and what we do with each.

| Status | What it means | What we do |
| --- | --- | --- |
| valid | The server accepted the address | Send |
| catch_all_valid | The domain accepts every address, and a second analysis found this one likely real | Send, in small numbers |
| catch_all_unknown | The domain accepts every address, and nothing could confirm this one | Hold, or send last |
| risky | Accepted, with warning signs | Hold |
| unknown | The server gave no clear answer (free in Layrcake) | Drop or recheck later |
| invalid | The server said the mailbox doesn't exist | Drop |

Catch-all is the one that trips people up. Some companies route mail for "non-existent or incorrect email addresses" to one shared mailbox, as Google Workspace describes the setting ([Google](https://knowledge.workspace.google.com/admin/gmail/advanced/get-misaddressed-email-in-a-catch-all-mailbox?hl=en)). Their server then accepts any address, real or not, so a plain check can't tell the two apart.

Unknown is the other honest answer. Under the email standard, a server answers each recipient with a code: 250 for accepted, 550 for "mailbox unavailable" ([RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.txt)). But servers may delay that judgement, and the standard notes that a recipient check "may return no information at all". Temporary refusals (4xx codes), which some servers use against unfamiliar senders, mean "try later", not "invalid" ([RFC 6647](https://www.rfc-editor.org/rfc/rfc6647.txt)).

## Should Claude guess email addresses?

No. Ask Claude for "the email of the head of sales at Acme" with no tools, and it may well answer `jane.smith@acme.com`, written with total confidence. It is a pattern, not a lookup. The standard leaves the part before the @ to each company's mail server to interpret ([RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.txt)), so there is no rule to guess from. And on a catch-all domain, a guess passes a basic check whether or not anyone reads it.

Put "don't guess addresses" in the prompt, or in a [skill file](https://layrcake.dev/guides/claude-cold-email) so it holds every time. Then every address on your list came from a finder and passed a check.

## What does finding emails with Claude cost?

At Layrcake's [prices](https://docs.layrcake.dev/pricing.html) in October 2026: 5 credits for each email found, nothing when none is found, and 1.25 credits for each check, with unknown answers free. A credit is $0.01. So 20 people with an 80% find rate cost about 80 credits to find and 20 to check, roughly $1 for the list.

> **Ask for the budget in the prompt.** Claude checks the cost of each call against the budget you give it and stops before it runs out. Misses cost nothing, so a list with gaps costs less, not more.

To go further than a list of addresses, the [lead generation guide](https://layrcake.dev/guides/claude-lead-generation) runs the full loop: find people, verify, research and draft. To connect Layrcake to Claude, see [the setup page](https://layrcake.dev/claude).

## FAQ

### Can Claude find someone's email address?

Not from its own knowledge. Claude needs an email-finding tool connected over MCP. With one, it looks up each person from their name and company website or LinkedIn profile, and returns the address with a status.

### Is Claude's email guess reliable?

No. Without a tool, Claude can only produce a likely-looking pattern such as first.last@company.com. It isn't a lookup, and on catch-all domains a guessed address passes a basic check whether or not it exists.

### What does catch-all mean in email verification?

The company's mail server accepts mail for any address at its domain, real or not. A verifier can't confirm the mailbox exists, so catch-all addresses are best sent in small numbers or after your valid ones.

### How much does it cost to find emails with Claude?

With Layrcake in October 2026, 5 credits ($0.05) per email found, nothing when none is found, and 1.25 credits per verification. A list of 20 people costs about $1.

---

Layrcake is go-to-market infrastructure for AI agents: one MCP server and API that lets Claude, ChatGPT, Cursor and Codex find leads, verify emails, read buying signals and run approved campaigns. Agents: see https://layrcake.dev/agents.md