Connect Plunk to send email from HARi

Plunk is an email-sending service you hold your own account with. Connecting it to HARi takes one value: paste your Plunk secret key into HARi, set the address your mail comes from, and every email HARi sends goes out through your Plunk account. Volume is unlimited as far as HARi is concerned — Plunk bills you, and nothing counts against your HARi plan allowance.

Choose Plunk over SMTP when you don’t have a mail server of your own, when your hosting provider blocks outbound mail, or when you want delivery statistics — opens, clicks, bounces — flowing back into HARi automatically.

Before you start: verify your domain in Plunk

Do this first. Plunk will not send anything for a domain it hasn’t verified, so a key pasted into HARi before the domain is verified produces failed sends and no obvious explanation. Plunk’s own documentation puts it plainly: “Verifying your domain is a requirement to send emails through Plunk” (Plunk, Verifying domains).

Sign in to Plunk and open your project’s settings.
Find the Domains section and add the domain you want to send from — for example yourcompany.com, or a subdomain such as mail.yourcompany.com.
Copy the DNS records Plunk shows you. Plunk tells you exactly what to add — typically three CNAME records for DKIM (the cryptographic signature that proves your mail is authorised), plus a TXT record on a sub-domain that bounces come back through. Each DKIM value is unique to your domain, so copy them exactly rather than retyping them.
Add them at your DNS provider. That’s whoever manages your domain: Cloudflare, GoDaddy, Gandi, OVH, your web host. Look for a page called DNS, DNS records, or Zone editor, and add each record with the type, name, and value Plunk gave you.
Wait for Plunk to confirm. It checks in the background and usually finishes within a few minutes, though DNS changes can take considerably longer to spread — Plunk allows up to 72 hours before giving up.

Tip — While you’re in DNS, add a DMARC record too: a TXT record named _dmarc with the value v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com. p=none means “monitor only, don’t change how you treat my mail” — it’s the safe setting, and Gmail and Outlook.com both now expect a DMARC record to exist for bulk senders. Tighten it to p=quarantine or p=reject later, once you can see your own mail passing.

Get your Plunk secret key

Every Plunk project has two keys, and only one of them can send email.

The public key is for recording events from a browser and cannot send anything.
The secret key is the one HARi needs. It carries full access to your Plunk project.

In Plunk, open your project and go to Settings → API Keys. Both keys are shown there; copy the secret one.

Important — Treat the secret key like a password: anyone holding it can send email as you and read your Plunk contacts. HARi keeps it in your own workspace’s database, never shared with any other workspace, and masks it in the settings screen once saved so it is not displayed back in full. One thing worth knowing before you rotate it: in Plunk the two keys are a pair, and regenerating invalidates both at once. If you rotate, come back and update the key in HARi straight away or your sending stops.

Connect Plunk to HARi

Open Settings → Email Sending in HARi (called Outbound Email in earlier versions).
Start the Plunk sender. What you see depends on whether this workspace has sent email before. On a brand-new workspace with no sender yet, the page offers a provider choice — pick Plunk. If a sender is already connected, that choice isn’t shown: click Connect Plunk next to Connected Mailboxes instead. The fields are identical either way. Adding a sender this way is an administrator action.
Paste your secret key into the Secret Key field.
Set your From address — the address recipients see the mail coming from. It must be on the domain you verified in Plunk; an address on an unverified domain will be refused. Add a From name as well, since a company or person name reads far better in an inbox than a bare address.
Save changes.
Send a test email to yourself from the same page and confirm it arrives. Do this before building a campaign, not after.

Feed delivery events back into HARi

Plunk knows things HARi can’t see on its own: whether a message was opened, whether a link was clicked, whether an address bounced. Point Plunk at HARi’s webhook — a private address that one system calls to notify another the moment something happens — and all of it flows back automatically, onto your contacts’ timelines and your campaign statistics.

In HARi, on the same Email Sending page, find the Plunk Webhook URL and copy it. It contains a private code unique to your workspace — HARi ignores delivery events that arrive without it, so treat the URL as confidential.
In Plunk, add a Webhook step to your workflows and paste the URL in.
Send another test and watch the Plunk Event Log in HARi. It refreshes on its own every 30 seconds. The first event arriving is your confirmation that the loop is closed.

Bounce feedback is the part that pays for itself. Without it, a dead address stays on your list and gets hammered on every send, which is precisely what wrecks a sender’s reputation. With the webhook connected, HARi marks the address and stops sending to it.

What this method costs you

Nothing on the HARi side. Mail sent through your own Plunk account is unlimited and never draws on your plan’s sending allowance or your credits — Plunk bills you for the volume, so HARi has no reason to meter it as well.

HARi hands each message straight to your Plunk account as it goes out; it does not hold campaigns back to a pace of its own on this route. Whatever sending limits apply are Plunk’s, on your account, so check them there before a large campaign.

That makes your list quality your own responsibility here, and it is worth taking seriously. Google’s sender guidelines tell every sender to “Keep spam rates reported in Postmaster Tools below 0.30%” (Google, Email sender guidelines) — a threshold measured against your domain once the mail leaves your own account. Two things keep you under it: send to people who asked to hear from you, and wire up the webhook below so bounced addresses are suppressed instead of being retried on every send.

When it doesn’t work

What you see	What it usually means	What to do
The key is rejected	You pasted the public key instead of the secret one	Go back to Settings → API Keys in Plunk and copy the secret key
Sends fail with no obvious reason	The From address is on a domain Plunk hasn’t verified	Verify the domain in Plunk first, then make sure your HARi From address is on that exact domain
The domain won’t verify in Plunk	A DNS record is missing, mistyped, or on the wrong domain	Re-copy each record from Plunk with copy/paste. Check you added them to the same domain you entered in Plunk — records on `yourcompany.com` will not verify `mail.yourcompany.com`
Sending stopped working overnight	The keys were rotated in Plunk, which invalidates both at once	Copy the new secret key from Plunk and update it in HARi
No events in the Plunk Event Log	The webhook isn’t wired up, or the URL was truncated	Re-copy the webhook URL from HARi and re-paste it into your Plunk workflow. Send a test and wait 30 seconds for the log to refresh
Opens and clicks never appear on contacts	Same cause — the events aren’t reaching HARi	Fix the webhook above; statistics start populating from the next send
Mail sends but lands in spam	DKIM is in place but DMARC isn’t, or your list needs cleaning	Add the DMARC record above, and make sure bounces are flowing back through the webhook so dead addresses stop being retried

HARi Email — the sending method included with your plan, nothing to sign up for
Outlook / Microsoft 365 — send as your real Outlook identity
Your own SMTP server — if your provider gives you SMTP credentials instead
Email sending allowance — why your own account is unlimited
Why are my emails not sending? — diagnosing a failed send