Build your cold email infrastructure with Claude

The video walkthrough goes up on my YouTube channel shortly. The written version below is the same thing, step for step.

What this actually does

First, the one rule everything else rests on: never prospect from your main address. Fifty identical emails a day from a mailbox that used to send five is not human behaviour, the providers start filtering it, and the reputation of the whole company domain goes with it, colleagues and clients included. Prospecting runs on dedicated domains and dedicated inboxes.

Building those by hand means a spreadsheet to size the volume, a registrar for the domains, DNS records to write, then each inbox to create and connect to the sending tool. The skill does it as a conversation, in order:

• It works out how many inboxes and domains you need, from the clients you want a month, the emails you send, or the inboxes you already have.
• It proposes free .com domains close to your brand, checked at the registry, and refuses anything that reads like phishing.
• It shows one recap, then buys the domains and creates the inboxes through the Mailpool API, which writes SPF, DKIM and DMARC itself.
• It pushes the inboxes into your sequencer and gives you the date the first real email can go out.

Every number comes from a script, never from the model doing arithmetic in its head. And nothing is bought before you say yes: every paid command prints the request first.

The rules it follows

• 20 prospecting emails per inbox per day, warmup not included. You need more volume, you buy more inboxes, you do not push the ones you have.
• 25 percent spare inboxes, kept warm, so an inbox that drops or a busy week never stops the sending.
• 3 inboxes per domain, and only .com. The number of domains comes from the volume, never from wanting choice: a domain bought just in case stays cold and is paid every year.
• 70 percent Google Workspace, 20 percent Outlook, 10 percent SMTP at most. Matching your prospects' own providers no longer pays, and Google lands best for now. But never 100 percent on one provider: the day it changes its rules, the other two rails are already warm.
• Warmup runs in the sequencer, not at Mailpool. An inbox bought today prospects at full volume around week 7, so the infrastructure is bought at least six weeks before a launch.

To check the method on your own numbers: 340 emails a day gives 17 inboxes, 22 with the spare, so 8 domains, split 5 Google Workspace, 2 Outlook and 1 SMTP.

Step 1. Create your Mailpool account

The skill talks to your Mailpool workspace and buys on your account, so you need one. This link gives you 10 percent off, on top of the discount Mailpool already publishes for annual billing. What a mailbox costs, provider by provider, is on the Mailpool page of this site.

That is an affiliate link, and I say so on my disclosure page. It costs you nothing more and it is the same product either way.

Step 2. Get your API key

In Mailpool, open the workspace settings, then API, and generate a key. The scripts send it in the X-Api-Authorization header and never print it.

Never paste the key into the conversation. It goes in a file called .env, next to the skill (step 3), on one line:

MAILPOOL_API_KEY=your-key

Step 3. Install the skill in Claude Code

Fill the form at the top of this page and I email you the download link. Unzip the file into ~/.claude/skills/: you get a folder cold-email-infrastructure, and the .env file from step 2 goes inside it.

It runs in Claude Code because the scripts call the Mailpool API from your own machine. They only need Python 3, which macOS and most Linux systems already have. Restart Claude Code, then type /cold-email-infrastructure, or simply ask it how many inboxes you need.

Step 4. Ask for your infrastructure

The skill asks where you start from: the clients you want a month, the emails you send a month or a day, or the infrastructure you already have. Starting from clients, it shows the whole funnel first, and that is often the most useful part: it tells you how many prospects one client costs you.

Then it reads your website, proposes the domains as a numbered list, and you answer with numbers. It asks for the sender's name and the domain owner, which registrars require, shows the recap, and waits for your yes.

Once the inboxes are active, it pushes them into your sequencer: PlusVibe, Instantly, Smartlead, lemlist, Reply, Saleshandy, Emelia, Warmbox or ReachInbox. For anything else, Mailpool exports a CSV.

What it does not do

• It does not write the emails, build the prospect list or launch the campaign.
• It does not check a domain's past. A free domain may have been burnt by a spammer years ago: for a name that looks too good, look it up on web.archive.org and the blocklists before buying.
• It does not check trademarks. For a domain close to someone else's brand, the brand owner's written approval is what protects you.

The order I do all of this in, from the first domain to the first email, is written up in six steps to stay out of spam.

Where I would start

The infrastructure is the easy half. The hard half is deciding who is worth writing to and what to say to them, and that is what I do all day. If you would rather not run the prospecting yourself, my agency runs it end to end, infrastructure included.

Fifteen minutes about your market and your offer, and I tell you what I would do. You run it in-house or you hand it to my team. It costs nothing either way.

Book the fifteen minutes Get the skill first