Chapter 1 of 8 · What Mailshake does at import
About this video
This video uses sample data, not real Mailshake data. BillionVerify is not affiliated with or endorsed by Mailshake. File verification needs a paid account.
Video transcript
What Mailshake does at import
Mailshake takes your CSV inside the campaign, and the file has to stay at one megabyte or less. Here's how to verify first and still fit. You don't build a list first in Mailshake. You import prospects while you create the campaign. Then a review page opens, and that's where its list cleaner sits. Click Open List Cleaner, and it runs in the background. Two labels come back. Bad is almost certain to bounce. Risky has a higher risk of bouncing, and may be a catch-all. Mailshake's own advice is strict. Take out both. You don't have to use it, though. If you verify with another tool, Mailshake lets you disable the cleaner in Team Settings. We'll verify before the file reaches Mailshake, because the download needs one extra step on its way in.
Verify the list
Add your CSV to File List Verify. It works through the list in the background, and emails you at the end. Then pick your statuses, and click Export Results, one file per campaign.
Fit the limit
Here's the catch. Your download keeps your columns, and adds 13 of ours. On a big list, that can push the file past the one megabyte limit. Mailshake's fix is to remove columns you don't need. Keep the email, the names, and anything you'll personalize with. Delete our columns. Still too big? Split the file. There's a prospect cap as well. 5,000 per campaign on Email Outreach, 10,000 on Sales Engagement. For a bigger list, duplicate the campaign, and upload a file to each. Then check the format. A header row, with no dashes or parentheses. One line of text in each cell. No blank rows or columns. One email per row. And a real CSV, not an Excel file.
Import into Mailshake
Open Campaigns, click New Campaign, then Prospects, and drop in the file. If someone's already in Mailshake, Add and update overwrites their details. Add only keeps what's there. The review page shows three things. Prospects in another campaign get imported by default, unless you click Remove. Unsubscribed prospects are left out. List cleaning is your call, since this file is checked.
Keep catch-all apart
Here's where we differ a little. Mailshake says remove Risky. If you'd rather try catch-all, give it a small campaign of its own, so a rise in bounces is easy to spot.
After launch
Want a whole company kept out? On the Unsubscribes page, import its domain with a star in front. That covers every address there. When an email bounces, Mailshake doesn't mark that recipient as paused. It does this instead, so the rest of the sequence never goes out.
What it costs
On our side, valid, invalid, catch-all and role take a credit apiece. Unknown, bad syntax and disposable don't. You'll need a paid account for file uploads, and one credit purchase is enough.
Get started free
20 free credits every day you use your account, up to 600 a month. No credit card required. Start at billionverify.com.
Featured in this video
Mailshake Email VerificationMailshake Email Verification explains why unverified imports hurt outreach domains and what to check before launch, including catch-all status and list age.Try Mailshake Email VerificationMore in Cold Email
All email verification videosBillionVerify pricing
Start free, then pay for what you verify. Pick a plan or buy credits once.
billed yearly $96
Save 60%$0.0004 / per credit
All 240,000 credits arrive at once. Use them anytime.
Choose your credits
Included in every paid plan
- 240,000 credits / year
- Single email verification
- Bulk email verification
- Email Finder
- Bulk Email Finder
- Company Search
- Live SMTP mailbox check
- Real-time API + batch processing
- CSV & Excel upload support
- Comprehensive verification reports
- Workspaces and teams with spend limits
- Credits never expire
Try the AI email verification features
20 free credits every day you log in, up to 600 a month. Free AI first email verification across every feature, no credit card.
Native MCP Server integration · Catch-all reported separately · Free tier, no credit card