Verify the leads in your Smartlead campaigns

Why check a campaign, not just a list

Leads sit in a campaign for weeks while people change jobs and companies change domains. An address that was fine when you imported it can bounce by the time the third follow-up goes out. Checking the campaign itself, right before a send or once a week, catches those addresses without exporting and re-importing a file.

How it works

1. Subscribe to Pro or Email + Phone, then open Campaign integrations in your dashboard.
2. In Smartlead, open Settings > API Keys and copy your API key.
3. Paste the key and click Connect. We check it with Smartlead before saving it.
4. Choose a campaign from the list. It is read live from your account.
5. Leave write-back off to only check the leads, or turn it on and pick what should happen to invalid leads.
6. Read the confirmation, which lists exactly what will happen, and start the run.
7. Open History to follow progress and download the results.

What we read and what we change

Only documented Smartlead API endpoints are used. To check a campaign, SimpleVerifier reads:

• GET /api/v1/campaigns/ lists your campaigns so you can pick one. docs
• GET /api/v1/campaigns/{id}/leads pages through the chosen campaign's leads, 100 at a time. docs

With write-back turned on for a run, and only once its verification has completed, it calls these for leads marked invalid. Nothing is written when write-back is off, when the run is canceled, or when you remove the key first.

• DELETE /api/v1/campaigns/{id}/leads/{lead_id} removes each invalid lead from that campaign, one call per lead. docs
• POST /api/v1/leads/add-domain-block-list adds the invalid addresses to your global block list. docs

• Smartlead's docs say that when a removed lead is not in any other campaign, it is also deleted from your Smartlead account. Leads that are in other campaigns stay there.
• Smartlead limits API calls per key (60 a minute on its standard tier), so SimpleVerifier paces its calls. A large campaign takes longer to read, and removing many invalid leads can take a while because each removal is its own call.
• Subsequences are left out of the campaign list, because their leads come from the parent campaign.

What the results mean

• Valid: the mail server confirmed the mailbox exists.
• Risky: it may work, but delivery isn't confirmed, for example a catch-all domain. Write-back never touches these; decide for yourself.
• Invalid: it will bounce, or it's a disposable address. These are the only leads write-back acts on.

The results file keeps each lead's email, name, company and Smartlead lead ID, so you can match rows back to the campaign.

Common questions

How do I verify the leads in a Smartlead campaign?

Connect your Smartlead API key in the SimpleVerifier dashboard, pick the campaign and start a run. SimpleVerifier reads the campaign's lead emails through the Smartlead API and checks each one with the mail server. Results appear in History as valid, risky or invalid with a reason, with the same downloads as an uploaded CSV.

Does SimpleVerifier change anything in my Smartlead account?

Not unless you turn on write-back for that run. With it off, SimpleVerifier only reads campaigns and leads. With it on, and only after verification has completed, it acts on leads marked invalid: it can delete these leads from the campaign and/or add these addresses to your Smartlead global block list. Risky leads, such as catch-all domains, are never touched.

How is my API key stored?

It is checked with Smartlead, encrypted with AES-256-GCM using a server-side key, and stored on our server. It is never shown again or sent back to your browser, and it is not written to logs. Removing the key in the dashboard deletes it, and any pending write-back is then skipped.

How many leads can one run check?

Up to 100,000 leads per run, the same limit as a CSV upload. Very large campaigns can take more than a day to finish, because mailbox checks run within a daily capacity; History shows how far a list has got.

Which plans include it?

Pro ($29.99/month) and Email + Phone ($49.99/month), with no per-lead charges. Pay-as-you-go credit packs do not include integrations; you can still export a CSV from Smartlead and upload it.

Why was my Smartlead key rejected?

A 401 from Smartlead ("Invalid API Key") means the key is wrong or has been regenerated. Copy it again from Settings > API Keys and reconnect.

Does it work with Smartlead client (agency) accounts?

It reads the campaigns your API key can see. Blocked addresses are added to your global block list; no client ID is set.