How to Upload Leads to a Smartlead Campaign From CSV (Verify First)

To upload leads to a Smartlead campaign cleanly, prepare the CSV first: one lead per row, plain headers, duplicates removed, and every email verified before the file goes in. Smartlead is the sequencer. It sends and rotates inboxes, but the quality of the list is decided before the upload. This post walks through the preparation in the order that saves the most time.

Format your file for Smartlead →

Why the upload is the cheap moment to fix a list

Once leads sit in a campaign, you are working under sending pressure. Inboxes are warmed, daily limits are set, and every invalid address that gets mailed is a hard bounce on a mailbox you are trying to protect. Before the upload, a bad row costs nothing: you delete it.

Smartlead's help centre also shows what fixing afterwards looks like. An uploaded CSV appears in the campaign's Upload History while the campaign is a draft, and a file can be deleted there, which removes that upload's send statistics too. Deletion requests are limited to 2 a day, at least 30 minutes apart (Smartlead help centre, read 9 November 2026). That is a workable safety net, not a workflow. A clean file avoids needing it.

If you have already seen bounces, our guides to Smartlead bounce rate and what to do when inboxes are hurt by a bad list cover recovery.

Step 1: Shape the file

Open the CSV in a spreadsheet and check the basics.

1. One header row, in row one, with plain names such as email, first_name, last_name, company. Avoid symbols, line breaks and duplicated header names.
2. One lead per row. If a company has three contacts, that is three rows.
3. One column per variable your copy uses. If the email says "I saw {{company}} is hiring", the company column must exist and be filled.
4. No merged cells, no formulas, no extra tabs. Export to CSV, not a workbook with notes.
5. UTF-8 encoding. Garbled accents in names are a sign the file was saved in another encoding. Fix garbled characters in CSV shows the repair.

The Smartlead lead CSV formatter does the header tidy-up in your browser. Smartlead decides how columns are matched on its own import screen, so confirm the mapping there rather than trusting any list of required headers from a blog post, ours included.

Step 2: Remove blanks and repeats

Three cleanups, in this order:

• Blank rows. Rows with no email crash nothing, but they eat attention. The remove blank rows tool clears them.
• Duplicates. The same address twice means two emails to one person, which looks careless and can raise complaints. Use the duplicate email remover.
• Blank variable cells. A lead whose first name is empty will get a gap in the opening line. Count how many rows are blank for each variable with CSV fill rate before mail merge and fill or drop them.

Do this before verification, so you do not pay checks on rows you were going to delete.

Step 3: Verify every address

Upload the cleaned file at /verify. SimpleVerifier runs real SMTP mailbox checks, not just syntax, and also flags catch-all, disposable and role addresses. Export the result in three groups:

Result	What it means	What to do in Smartlead
Valid	The mailbox accepted the check	Upload to your main campaign
Risky	Often a catch-all domain, where the server accepts any address	Separate campaign, lower daily volume
Invalid	The mailbox does not exist or the domain cannot receive mail	Do not upload. Keep for suppression

Catch-all domains accept every address at the SMTP step, so no verifier can confirm a single mailbox there. This is true of every tool, ours included. Our guide to what to do with catch-all emails covers the options.

Step 4: Upload and confirm the mapping

In Smartlead, open the campaign, go to its lead list and choose the CSV upload. On the mapping screen:

• Check that your email column is mapped to email.
• Check first name, last name and company map to the standard fields if you use them.
• Check each extra column is kept as a custom field under the name your copy uses.
• Leave out columns your campaign does not need, such as source notes.

Run the preview of one email with a real lead's data before you start the campaign. If a variable shows as blank, the column was not mapped or the cell is empty.

Step 5: Keep suppression in one place

Put the invalid rows from your verification export into a suppression file. That way, next month's upload does not bring them back from a fresh scrape. See suppression list from Smartlead for how to build one from your sending history.

Where each type of leads file comes from

Different sources produce different mistakes:

• Scraped or finder exports often have good emails but messy company names. Clean the names before they land in a subject line.
• Old CRM exports contain addresses that were fine two years ago. Verify, always. The email list decay calculator shows how fast a list ages.
• Purchased lists need the most care. Check a sample first with the email list sampler, and compare sources with find which list source caused bounces.
• Event or form lists are usually fresh, but typos like gmial.com are common. Verification catches them.

Re-verifying a list you uploaded weeks ago

Addresses go stale. If a list has been sitting for a month or more, verify it again before adding it to a new campaign. Mailboxes close, people change jobs, and domains lapse. A re-check before each campaign costs far less than a damaged inbox.

What SimpleVerifier costs next to doing this by hand

Verifying a file before every upload is only practical if checks are cheap. SimpleVerifier Pro is $39 a month (or $390 a year), with the first 100,000 checks a month at full speed, then slower, never cut off. Per the pricing page, Pro also includes:

• CSV upload, up to 100,000 rows per file
• Real SMTP mailbox checks, not just syntax
• Catch-all, disposable and role-address detection
• Export valid, risky or invalid separately
• An email finder and website enrichment
• API: 10,000 calls a month included, then $1.50 per 1,000

Only email verification has the 100,000 full-speed fair-use line. The finder and API are not unlimited. We do not publish accuracy percentages. Test a sample of your own data and judge from the result.

A short pre-upload checklist

1. Headers are plain and in row one.
2. One lead per row, no merged cells.
3. Blank rows and duplicates removed.
4. Every variable column filled or the rows dropped.
5. File verified. Invalid rows out, risky rows in a separate campaign.
6. Mapping confirmed on the import screen.
7. One test email previewed with real data.

Quick answers

• Does Smartlead verify emails for me? Check inside your Smartlead account for what it offers. Verifying the file before upload works regardless, and keeps the invalid rows out of the campaign entirely.
• Is there a row limit? Confirm limits on Smartlead's own upload screen and help centre. Our upload takes up to 100,000 rows per file.
• Can I use the same file for Instantly? Mostly yes. See Instantly CSV upload for that tool's mapping, and the Instantly and Smartlead hygiene checklist for what both share.

Try it on your own list

Upload the file at /verify. The first 100 checks are free with a Google sign-in, no card.

Pro, $39 a month: Unlimited email verification.* Never metered, never cut off. See pricing.

*Fair use: the first 100,000 checks a month at full speed, then slower, never cut off.