How to import and validate large b2b prospect lists efficiently in Verifycatchall

If you’ve ever stared at a spreadsheet with 10,000+ email addresses and wondered “How am I supposed to clean up this mess?”, this guide’s for you. Maybe your CRM is full of junk, maybe your sales team just bought a list (not judging, just saying), or maybe you’re just tired of bouncing emails making you look bad. Whatever the reason, you need to get your prospect list into shape—fast, and without losing your mind.

Let’s walk through how to import and validate big B2B prospect lists in Verifycatchall without getting bogged down in gotchas, slow processing, or confusing error messages. I’ll keep it straight, skip the hype, and point out where you can save yourself a bunch of headaches.


Step 1: Prep Your Prospect List

You can’t just dump a random spreadsheet into any validation tool and hope for the best. Garbage in, garbage out. Here’s how to get your list ready:

1.1 Clean Up Formatting

  • Use a CSV file. Pretty much every tool (including Verifycatchall) likes CSVs. Excel files can work, but CSVs are safer.
  • Make sure you’ve got one email per row. If your list has columns for names, company, etc., that’s fine—just make sure there’s a clear “Email” column.
  • Fix weird characters. Sometimes exported lists have hidden spaces, line breaks, or funky symbols. Clean these up, or you’ll get import errors.
  • Remove duplicates. No sense paying to validate the same address twice.

Pro tip: Open your CSV in Google Sheets or Excel, sort by the email column, and use “Remove duplicates.” Simple, but saves money and hassle.

1.2 Trim Down to What Matters

  • Extra columns (like phone, job title) won’t hurt, but ask yourself: do you really need them here? The more streamlined, the fewer things that can break.
  • If your list is split across multiple files, combine them first. One big upload is easier to track than 12 smaller ones.

Step 2: Import to Verifycatchall

Now that your list’s tidy, let’s get it into Verifycatchall.

2.1 Log In and Find the Right Feature

  • Log in to your Verifycatchall account.
  • Head to the “Bulk Validation” or “List Validation” section—names might differ, but look for something like “Upload List” or “Import CSV.”

Honest take: Some tools bury this behind a couple of menus. If you're lost, just use their search bar or help docs.

2.2 Upload Your File

  • Click the upload button and select your CSV file.
  • Map your columns. Verifycatchall will often ask you to confirm which column has emails. Double-check this—sometimes it guesses wrong, especially if your column is named something odd like “work_email.”

Pro tip: If your file’s huge (think 100,000+ rows), split it into chunks of 20k-50k rows. Most web tools, including Verifycatchall, can choke on gigantic files and either timeout or fail silently.

2.3 Check for Import Errors

  • After uploading, Verifycatchall will usually show a quick summary: number of emails detected, columns mapped, etc.
  • If you see a big mismatch (like “0 emails detected” when you know there are thousands), go back and check your CSV for typos, empty columns, or weird formatting.

Step 3: Validate Like a Pro

This is where the magic happens—or where things can go sideways if you’re not careful.

3.1 Start the Validation

  • Hit the “Start Validation” or equivalent button.
  • The system will queue up your list and start grinding through it.

What to expect: For lists under 10,000, you might get results in minutes. For 50k+, it could take an hour or more. Don’t sit there staring at the screen.

3.2 Understand the Results

When validation’s done, you’ll get a file with results. Usually, it’ll have columns like:

  • Valid: The email is real and deliverable.
  • Invalid: Hard bounce, typo, or just plain fake.
  • Catch-All: The domain accepts all emails, so status is uncertain.
  • Disposable/Role-based: Temporary or generic inboxes (think “info@” or “sales@”).

Honest take: No tool—including Verifycatchall—can 100% guarantee the accuracy of “Catch-All” emails. If you’re sending to those, expect some bounces.

3.3 Filter and Export

  • Download the results as a CSV.
  • Filter out the “Invalid” and “Disposable” emails before you load anything into your CRM or outreach tool.
  • For “Catch-All” results, use your judgment. If you have budget for a little risk, you might keep them—but don’t expect perfection.

Pro tip: Always keep your original list and your validation results. That way, if you need to check or re-run anything, you’re not starting from scratch.


Step 4: What to Watch Out For

Here’s where people usually trip up:

4.1 File Size Limits

  • If your file is too big, the upload will fail or freeze. Stick to smaller chunks (20k-50k rows).
  • Don’t trust that “no file size limit” claim. Even if the tool says so, your browser or internet connection might have other ideas.

4.2 Data Privacy

  • Don’t upload sensitive info you don’t need to. Stick to just emails (and maybe company/domain if you must).
  • Check if your company has rules about where you can upload customer data.

4.3 Cost Creep

  • Most validation tools charge per email, not per file. Duplicates and bad formatting mean wasted money.
  • Some tools will charge you for every row, even if it’s blank or obviously invalid. Double-check your list before uploading.

4.4 False Positives/Negatives

  • No tool is perfect. Some valid emails will be flagged as invalid (and vice versa).
  • “Catch-All” domains are always a gray area. Don’t blame the tool—blame the way those mail servers are set up.

Step 5: Best Practices for Ongoing List Validation

Cleaning your list once is good. Keeping it clean is better.

  • Validate before every big campaign. Don’t rely on last month’s results—emails go stale fast.
  • Automate if you’re doing this regularly. Verifycatchall has APIs. If you’re technical (or have a dev handy), set up a script to validate new leads as they come in.
  • Track your bounce rates. If you’re still getting a lot of undeliverables after validation, something’s wrong—go back and check your process.
  • Respect opt-in rules. Valid emails aren’t the same as opted-in ones. Don’t spam people, or you’ll end up on blocklists.

Quick FAQ

Can I upload Excel files (.xlsx) directly?
Sometimes, but CSV is safer. Excel can hide weird formatting that messes up imports.

What about international (non-English) emails?
Most tools handle them fine, but watch out for non-standard characters.

Do I need to keep old validation files?
Yes. Always. They’re your backup when something goes wrong.

How much does this cost?
Depends on your list size and Verifycatchall’s pricing. Always de-dupe before uploading.


Keep It Simple and Iterate

Here’s the bottom line: don’t overthink it. Clean your CSV, upload in reasonable chunks, filter your results, and move on. The more you try to outsmart the validation process, the more likely you’ll trip yourself up. Use tools like Verifycatchall to do the heavy lifting, but always sanity-check the results and keep things tidy.

You’ll get faster, cleaner results every time—and spend less time cleaning up messes down the line.