The moment someone pays for your platform, they get a welcome email from your own professional domain, automatically. By the end of this, that whole thing runs itself. No manual sending, ever.
Here's the plan
Authenticate your domain for email
Set your professional sending address
Create your Systeme.io API key
Connect Stripe so every paying customer gets tagged, by chat
Build the welcome-email automation
Test a real $0 signup, end to end
Campaigns and growth strategies come next week. This week, we get the engine running.
Two things to understand first
Two different domain jobs
Vercel made your site load at your domain. This makes your emails send from your domain. Same domain, a different set of DNS records. That's called email authentication.
The API key + the webhook
The API key is the login that lets your app add people to Systeme.io. The webhook is the trigger that fires when someone pays. Together: pay → tag → welcome email.
1
Authenticate your domain for email
This lets Systeme.io send email from you@yourdomain.com instead of a generic address.
In Systeme.io: Settings → Custom domains (or Emails)
Add the domain you bought in Video 1
Systeme gives you a few DNS records (mostly CNAMEs, plus a DMARC record), add exactly what it shows you
Add those records at your domain provider (where you bought the domain), then come back and verify
Important: this is NOT the same as connecting your domain to Vercel. Vercel made your site live. This is a different set of records that lets Systeme.io send email from your domain. Same domain, different job.
👉 What this is called: email authentication. The records prove your mail is really from you, mainly DKIM (the _domainkey signature records) and DMARC (protects your domain from being spoofed). Systeme.io gives them as CNAME and TXT records, just copy exactly what it shows.
✓ Done when: Systeme.io shows your domain authenticated / verified.
2
Set your professional sending address
In Systeme.io: Settings → Emails → set your "from" address, e.g. hello@yourdomain.com
Now every email comes from you, not a random address, which is what keeps you out of spam and looks legit
👉 This sends from your domain. If you want to receive replies at that address, you'd add a mailbox like Google Workspace later. Not needed today.
3
Create your Systeme.io API key
In Systeme.io: Settings → Public API Keys → create a key
Copy it and keep it handy, you'll paste it into Vercel in the next step
👉 This is the "API" piece. It's the key that lets your platform add and tag contacts in Systeme.io.
✓ Done when: you have your API key copied.
4
Connect Stripe so every payment tags them
You don't build this by hand. Paste this into Claude and let it build the connection:
Paste into Claude
When someone purchases a subscription on my platform through Stripe, add their email to Systeme.io as a contact and tag them "Member" (or whatever tag I choose), so I can trigger a welcome-email automation off that tag. Stripe is already set up and its keys are already in Vercel, reuse the existing Stripe setup. Build it end to end, verify the Stripe webhook so it's secure, use an environment variable for the Systeme.io API key, and don't ask me questions, make reasonable choices yourself. When you're done, tell me: the exact name of the Systeme.io environment variable to add in Vercel, and exactly where to point the Stripe webhook in my Stripe dashboard.
Then finish the two manual pieces Claude hands you:
Add your API key in Vercel → Settings → Environment Variables as SYSTEME_API_KEY
In Stripe, add the webhook endpoint Claude gives you (Developers → Webhooks → Add endpoint), then copy its signing secret into Vercel
Redeploy after adding the key. Environment variables only take effect on a new deployment. Add the key, then redeploy in Vercel, or it won't work.
✓ Done when: Claude confirms it's built, and SYSTEME_API_KEY + the webhook secret are in Vercel.
5
Build the welcome automation
Now the tag needs to actually do something. Set up the automation in Systeme.io:
In Systeme.io: Automations → Rules → Create
Trigger: "Tag added" → your tag (e.g. Member)
Action: "Send email" → your welcome email
Write a short, warm "Welcome to the community" email, what they get, and their first step
👉 The tag is the bridge. Stripe tags them, and the tag triggers this email. That's the whole loop.
✓ Done when: adding the tag to a test contact sends you the welcome email.
6
Test it, end to end
Go to your live site and run a $0 test signup (use the 100%-off coupon you made in Video 2)
Confirm in Systeme.io: Contacts → the person is there, with your tag
Confirm the welcome email lands in the inbox, from your domain
A green build proves nothing. The only proof is a real signup that ends with the welcome email in the inbox. Do that before you call it done.
By the end of this video
The engine is running.
Your domain is authenticated for email
Every paying customer is tagged automatically
They get a welcome email from your professional domain, hands-off
Next week: campaigns, sequences, and the growth strategies to actually fill this engine and keep people coming back.