Clean a Smartlead Campaign Before You Send: Verify Leads in Place

To clean a Smartlead campaign before you send, connect a Smartlead API key on SimpleVerifier's Integrations page (/connect), pick the campaign and press Verify leads. Every lead is checked in place. By default, risky and invalid leads get sv_status and sv_verified_at in their custom fields, and nothing is paused or removed. If you want Smartlead to stop emailing invalid leads, tick Pause invalid leads in this campaign, which you can undo later.

Do it a day before launch. Smartlead's API limits make write-back on a big campaign slow, and that is the main thing people do not expect.

Step 1: get the Smartlead API key

In Smartlead, open your profile menu, then Settings > API Key Management. Under Admin API Keys, press + Create API Key, name it (for example simpleverifier), press Create and copy the key at once: Smartlead shows the full key only once. Smartlead's API reference covers the endpoints.

Step 2: connect and pick the campaign

Paste the key on Integrations and choose the campaign. Smartlead's API has no lead lists and no workspace name, so you pick from campaigns only. The confirm screen shows the cost before the run: one check per distinct address, from your free checks or your plan. The Smartlead integration page lists every call made.

Step 3: choose the write-back

Option	Default	What it does in Smartlead	Reversible
Tag risky and invalid leads	On	Writes sv_status and sv_verified_at into custom fields	Yes, it is just a field
Pause invalid leads in this campaign	Off	Stops their scheduled emails in this campaign	Yes, resume the lead in Smartlead
Delete invalid leads from this campaign	Off	Removes them; a lead in no other campaign is also deleted from the account (per Smartlead's docs)	No
Add invalid addresses to the global block list	Off	Applies to every campaign in the account	Remove the entry by hand

Valid leads are not tagged. That is deliberate: tagging is one API call per lead, and leaving valid leads alone saves most of the calls. After a run, a lead with no sv_status was checked and came back valid.

Risky leads are tagged but never paused, deleted or blocked. Catch-all domains and servers that will not confirm a mailbox land there. Our catch-all decision framework helps you decide what to do with them.

Step 4: plan around Smartlead's API limits

Smartlead's standard API limit is 60 calls a minute and 1,000 an hour per key. Pulling leads takes one call per 100 leads, so reading is fast. Tagging, pausing and removal take one call per lead. A campaign with 3,000 risky and invalid leads needs about 3,000 write calls, which at 1,000 an hour is about three hours. Pausing as well doubles that.

So the order that works:

1. Run the check a day before the campaign starts.
2. Look at the counts under Recent runs on the Integrations page.
3. If invalid leads are a large share, pause them, or fix the source before launch.
4. Start the campaign once write-back has finished.

Run 100 free checks on one Smartlead campaign to see the tags before you commit a large one.

What else to check before sending

Verification removes addresses that would hard bounce. It does not warm inboxes or fix authentication. Before a launch, also read our guide to preparing a lead list for Smartlead, and check your sending domain with the deliverability check. If verified addresses still bounce, see why verified emails still bounce.

Keep the campaign clean after launch

Leads added later are not covered by a one-off run. On paid plans, Auto-verify new leads daily checks only addresses it has not seen in that campaign, once a day. See pricing for which plans include it.