What your email verification results mean

When you verify an email list, WarmySender labels each address with one of four results — Valid, Risky, Unknown, or Invalid. This guide explains what each result means and exactly what to do next, so you can send confidently and protect your sender reputation. The short version: clean out the addresses that don't exist, and send the rest with warmup running on your mailbox.

WarmySender is a 4-pillar outreach platform — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel sequences. The Email Verifier is part of Cold Emailing: clean your list before you send so more of your messages reach the inbox.

At a glance

Valid — safe to send

A Valid result means we confirmed the mailbox exists and is able to receive email. These are your safest addresses, and they're the ones to send to first. Verifying a list before you send keeps your bounce rate low, which is one of the biggest factors in whether your future emails land in the inbox.

Even with Valid addresses, sending through a mailbox that has warmup running is the best way to keep your reputation strong as your volume grows.

Risky — catch-all or uncertain

A Risky result most often points to a catch-all domain — one set up to accept mail sent to any address at that domain, whether or not the specific mailbox exists. Because the domain says yes to everything, we can't tell you for certain whether this exact person's mailbox is real, even though the domain itself is live.

Risky addresses are often perfectly fine to email. The safe way to reach them is with warmup enabled on your sending mailbox, so that if a few don't land, your sender reputation stays protected. For an important list, you can also re-check Risky addresses later.

Unknown — we couldn't confirm either way (and it's free)

This is the result people ask about most, so here it is plainly: Unknown means we couldn't confirm the address either way — it does not mean the address is bad. Some receiving mail systems, especially large, security-conscious businesses and Microsoft-protected domains, deliberately refuse to reveal whether any given mailbox exists. When a receiving system keeps its answer private like that, the honest result is Unknown rather than a guessed Valid or a false Invalid.

Two things make Unknown easy to work with:

• It's free. Unknown results never count toward your monthly verification limit — you're only charged for results we could actually confirm.
• It's usually safe to email. Many Unknown addresses are real and reachable; the receiving system simply wouldn't say so. Send them with warmup running on your mailbox and your reputation stays protected.

We made this choice on purpose: we'd rather tell you we couldn't confirm an address than label a genuine, reachable prospect as bad and have you skip them.

Invalid — the address doesn't exist

An Invalid result means the address itself doesn't exist or can't receive mail — for example, a typo, a mailbox that was closed, or a domain that no longer accepts email. You should skip Invalid addresses entirely.

Removing Invalid addresses before you send is the single most valuable thing verification does for you. Sending to addresses that don't exist is what drives up your bounce rate and damages your sender reputation — exactly the harm that cleaning your list first is meant to prevent.

How to send based on your results

A simple, reputation-first way to act on a verified list:

• Send Valid first. Start with your confirmed Valid addresses. They're the safest to send to and a clean way to begin any campaign.
• Send Unknown and Risky with warmup enabled. These are usually fine to email — just make sure warmup is running on the mailbox you send from, so your sender reputation stays protected if a few don't land. (See how to control your warmup sending volume.)
• Re-check borderline results for high-stakes lists. For your most important outreach, it's worth re-checking borderline Unknown or Risky addresses before you send — receiving systems can answer differently at different times, so a fresh check sometimes resolves to a clearer result.

The one result to act on differently is Invalid — skip those addresses entirely. Everything else is sendable when warmup is running on your mailbox.

Using your verified results in a campaign

Once a verification finishes, you don't have to sort the results by hand or download and re-upload a spreadsheet — and you don't have to worry about your existing lists or campaigns being changed. WarmySender turns your results into a clean list you can launch a campaign to in one click, and it never edits your original list or touches your existing campaigns, so nothing is duplicated and no one is contacted twice.

• A clean list of the good addresses, ready for a campaign. The Valid and Risky addresses — the ones that are good to email — are gathered into a brand-new list named after your original with “- Verified” on the end. It's a separate list you can point a campaign straight at, so you can send to just the good addresses in one click.
• Uploaded a CSV? Just click “Create clean list”. Verifying a CSV you uploaded works exactly the same way — when it finishes, a Create clean list button builds the very same ready-to-use list of Valid and Risky addresses. So a one-off spreadsheet becomes a campaign-ready audience with a single click. You do not need to download the results and re-upload a trimmed CSV; existing contacts are reused automatically, so there are never any duplicates.
• Your original list and campaigns are left exactly as they were. The verified list is created alongside your original — nothing is moved, merged, or overwritten, and no existing campaign is changed. Because the good addresses are a fresh list rather than an edit to something already sending, there's no risk of duplicating anyone or emailing a contact twice. Anyone already in your account is reused rather than added again, and addresses that came back Invalid are quietly kept out of sending so your campaigns skip them.
• You can also download the full results as a CSV. Prefer a spreadsheet, or want to import elsewhere? Every finished list has a Download option that gives you a CSV of every address with its result. Use the ready-made verified list for a one-click campaign, or the CSV to handle the results yourself — whichever suits you.

Frequently asked questions

What does an "Unknown" verification result mean?

Unknown means we couldn't confirm the address either way — not that it's bad. Some receiving mail systems, especially heavily protected business and Microsoft-protected domains, won't reveal whether a specific mailbox exists, so we can't return a definite yes or no. An Unknown result is free (it doesn't count toward your monthly verification limit), and these addresses are usually safe to email as long as warmup is running on your sending mailbox. Many Unknown addresses are perfectly real; the receiving system simply kept its answer private.

Do Unknown results count toward my monthly verification limit?

No. Unknown results are free and never count against your monthly verification allowance. You're only charged for results we could confirm. Because Unknown addresses are commonly caused by the receiving side keeping its answer private rather than by anything wrong with the address, we don't think it's fair to bill you for an answer we couldn't give.

Is it safe to email an address that came back as Unknown?

Usually, yes — provided warmup is running on the mailbox you send from. An Unknown result is not a sign the address is bad; it just means the receiving system wouldn't confirm it. The safe approach is to send your confirmed Valid addresses first, then include Unknown (and Risky) addresses with warmup enabled so your sending reputation stays protected. For very high-stakes lists, you can re-check borderline addresses later, since some receiving systems answer differently at different times.

What's the difference between Risky and Invalid?

Risky usually means a catch-all domain — one set up to accept mail for any address — so we can't single out whether that specific mailbox exists, even though the domain is live. Risky addresses are often fine to email with warmup on. Invalid means the address itself doesn't exist or can't receive mail, so you should skip it; sending to Invalid addresses is the main thing that hurts your sender reputation, which is exactly what verification helps you avoid.

Why are some of my results Unknown when other tools say the address is valid?

Different checks ask the receiving mail system in different ways and at different moments, and some receiving systems — particularly large, security-conscious and Microsoft-protected domains — deliberately give the same neutral answer to everyone. When that happens, the honest result is Unknown rather than a guessed Valid or a false Invalid. We'd rather tell you we couldn't confirm than label a real, reachable address as bad. Unknown results are free and are usually safe to email with warmup on.

What should I do with each result?

Send your Valid addresses first — they're confirmed and safe. Send Unknown and Risky addresses too, but with warmup enabled on your sending mailbox so your reputation stays protected. Skip Invalid addresses entirely, since those don't exist. For high-stakes outreach, it's worth re-checking borderline Unknown or Risky results before you send, as receiving systems can answer differently over time.

How do I use my verified emails in a campaign?

You don't have to download and re-upload anything. When a verification finishes, WarmySender gathers the Valid and Risky addresses (the ones that are good to email) into a new, ready-to-use list named after your original with “- Verified” on the end — and you point a fresh campaign straight at that list in one click. This works whether you verified an existing list or a CSV you uploaded: for a CSV upload, a Create clean list button builds the very same campaign-ready list. Your original list and existing campaigns are never edited, anyone already in your account is reused (so there are no duplicates and no one is contacted twice), and addresses that came back Invalid are kept out of sending. Prefer a spreadsheet? Every finished list also has a Download option that gives you a CSV of every address and its result.

Do verified results update my existing lists and campaigns automatically, or do I re-upload the CSV?

Neither is forced on you — you get both options, and your existing lists and campaigns are never edited behind your back. When a verification finishes, WarmySender automatically gathers the Valid and Risky addresses (the ones that are good to email) into a new, ready-to-use list named after your original with “- Verified” on the end. That new list sits alongside your original — nothing is moved, merged, or overwritten, and no existing campaign is changed — so you can point a fresh campaign at just the good addresses with no risk of duplicating anyone or emailing a contact twice. This applies to CSV uploads too: after a CSV finishes verifying, a Create clean list button builds the same ready-to-use list, so you never have to download the results and re-upload a trimmed spreadsheet. (Addresses that came back Invalid are quietly marked so your campaigns skip them, and existing contacts are reused rather than duplicated.) If you'd rather work in a spreadsheet, every finished list also has a Download option that gives you a CSV of every address and its result. Use the ready-made verified list for a one-click campaign, or the CSV to handle the results yourself — whichever you prefer.

Related reading

• How to control your warmup sending volume — Set the daily volume and ramp so you can send Unknown and Risky addresses safely
• Why was this prospect skipped? — How a known-bad address is handled so it doesn't hurt your sending
• Deliverability resources — How clean lists, warmup, and authentication keep you in the inbox
• Full documentation — Cold Emailing, Email Warmup, LinkedIn Outreach, and Multichannel guides