What a Typical Email Verification Run Actually Returns

Run a list through OS-Tools and you'll get your CSV back with every row preserved — plus two new columns appended on the right: status and deliverable. The status is one of three values: safe, risky, or invalid. The deliverable flag is a plain yes or no. That's it.

This article shows you exactly what that output looks like, what the numbers usually look like for a real list, and what to do with each bucket.

If you want to follow along with your own list, OS-Tools Email Verifier costs 1 credit per address — 200 free credits on signup — and returns a clean CSV in minutes for most list sizes.

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Quick start: Verify your list free → os-tools.com/tools/email-verifier

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What the output CSV looks like

OS-Tools keeps your original CSV intact. Whatever columns you uploaded — name, title, email, company, website, anything — all come back untouched. Two new columns are appended on the right:

name	title	email	company	website	status	deliverable
Jane Smith	Head of Ops	jane@acme.com	Acme Inc	acme.com	safe	yes
John Doe	CEO	john@oldco.net	OldCo	oldco.net	invalid	no
Info Desk	—	info@company.co	Company Co	company.co	risky	yes

The two appended columns: status (safe, risky, or invalid) and deliverable (yes or no). Use them together — status tells you how the verifier classified the address, deliverable is your plain yes/no on whether it's worth sending to.

The three statuses

Safe — the address is confirmed valid, the mailbox accepts mail, and nothing suspicious flags it. deliverable: yes. Send to these.

Risky — the verifier got an ambiguous response. Usually this means the domain uses a catch-all server (it accepts everything without confirming individual mailboxes exist), or the address has characteristics associated with low engagement. These won't always hard-bounce, but they'll hurt your deliverability over time. Don't send cold without a deeper check.

Invalid — the address is dead. The domain doesn't exist, the mailbox doesn't exist, or the SMTP handshake hard-rejected it. deliverable: no. Sending to these is guaranteed to bounce. Cut them.

In practice: a 5,000-email newsletter list

Take a typical 5,000-email list that a newsletter operator has been building for 18 months — a mix of organic signups, a few content giveaways, and one small list purchase from early on. Nothing obviously dirty, but nothing recently cleaned either.

Upload the CSV to OS-Tools Email Verifier, let the job run (usually a few minutes for a list this size), and here's the kind of breakdown you'd see:

Status	Count (example)	% of list	Action
Safe	3,250	65%	Keep — send normally
Risky	500	10%	Run through Verify+ or cut
Invalid	1,250	25%	Cut — remove from all lists

What this tells you: A quarter of the list is already dead. Sending to all 5,000 would push your hard bounce rate to around 25% — most ESPs suspend accounts above 2%. You'd also be dragging the risky addresses along, which burns your sender reputation even when they don't hard-bounce.

After the cut, you're sending to 3,250 confirmed-safe addresses (plus any risky ones you rescue via Verify+). Smaller list, healthier list.

What to do with each bucket

Safe (3,250): Drop straight into your ESP. These are your real audience.

Risky (500): Don't send cold. Run them through Verify+ for a deeper verification pass. Verify+ uses a different verification engine with better catch-all resolution — it'll rescue the ones that are actually good and confirm which ones to drop. Credits refunded for any it can't definitively clear.

Invalid (1,250): Delete. Don't archive "in case" — every send to a dead address adds to your bounce count.

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Ready to see your own breakdown? Run your list through OS-Tools → os-tools.com/tools/email-verifier — 200 free credits when you sign up.

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How clean is clean enough?

A healthy list for cold outreach or newsletter sends usually looks like:

• Hard bounce rate under 2% after cleaning (i.e. every invalid address removed)
• Risky rate under 10% of what you send to

If your safe rate after verification comes back below 50%, the list is in rough shape — usually a sign it's old, purchased, or scraped. You can still work with it, but you'll want to warm your domain carefully before any large send.

If your safe rate is 80%+, you're in good shape. Clean lists from consistent opt-in sources tend to land here.

When does a verification run not tell the whole story?

There are limits. A catch-all domain will always return risky until you run a deeper check. Verification also can't tell you whether an address is engaged — a safe address that hasn't opened an email in two years will still hurt your deliverability, just more slowly.

For that, you need engagement data from your ESP. Verification handles structural health. Engagement health is a separate problem.

Start with your free 200 credits

Sign up at OS-Tools, upload a sample of your list (CSV, one email per row — plus whatever other columns you want preserved), and you'll see your own status breakdown in minutes. The output is a clean CSV with your original columns plus the two new ones, ready to sort and act on.

200 credits is enough to verify 200 addresses — enough to get a real read on list health before committing to a full run.

Start verifying free → os-tools.com/tools/email-verifier

— James