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Email Verifier is the difference between 1% bounce rate and 12% bounce rate. This walks through single and bulk verification, the status codes that matter, and the cleanup rules that protect sender reputation.
Who this is forAnyone running cold outreach who imports lists from third parties, scrapers, or old CRM data. If your list is older than 90 days, half of it is already stale — verify before sending.
What you'll need
Step 1
Hunter → Email Verifier → paste an email → Verify. Returns status in 2-5 seconds.
In Hunter, click Email Verifier.
Paste a single email. Click Verify.
Hunter runs: format check, MX record lookup, SMTP handshake, mailbox ping.
Returns one of: Valid, Accept-all, Invalid, Unknown.
Step 2
Valid = safe to send. Accept-all = risky. Invalid = do not send. Unknown = verification timed out.
Valid: deliverable. Mailbox exists. Safe to send cold.
Accept-all: domain accepts ALL emails regardless of validity. Email "delivers" but may go to a black hole. Risky for cold (counts as deliverability noise even when nobody reads).
Invalid: mailbox does not exist OR DNS broken. Do not send — will bounce.
Unknown: verification could not complete (server slow, anti-spam, rate limit). Re-verify in 30 min or skip.
Step 3
Bulks → Email Verifier → upload CSV with one email per row. Hunter processes thousands at once.
For lists over 20 emails, use Bulks.
Bulks → Email Verifier → upload CSV. Required column: email.
Hunter processes in batches of ~100/minute. A 1,000-email list takes ~10-15 minutes.
Costs 1 verification credit per row, regardless of result.
Returns CSV with original data + verification status.
Step 4
Open the result CSV in Sheets. Filter to Valid only for cold sends. Keep Accept-all in a separate "review" list.
Open the Hunter result CSV.
Filter status column: Valid only. Save as your "send-safe" list.
Filter status: Accept-all. Save as "review" list — these MAY be deliverable but bounce-free is not guaranteed. Use for warmer audiences (existing customers) but not cold.
Filter status: Invalid. Delete or quarantine permanently.
Filter status: Unknown. Re-verify in 30 minutes or skip.
Step 5
Emails decay ~3-5% per quarter. A list verified 6 months ago is now 10-20% stale. Set a quarterly verification cadence.
Email decay is real: people leave jobs, change domains, mailboxes get disabled.
For lists used in active cold-outreach campaigns: re-verify every 90 days minimum.
For CRM contact records sent transactional emails: re-verify annually.
Set a calendar reminder. Skipping leads to a 5-10% bounce rate creep over 6 months.
Common mistakes
Sending to Accept-all emails as if they were Valid
What goes wrong: 30-50% of Accept-all emails go nowhere. Reply rates drop. Sender reputation slowly tanks because mailbox providers see no opens or replies on those sends.
How to avoid: For cold outreach: send only to Valid. Accept-all goes in a separate "warm audience" list for existing relationships.
Not re-verifying old lists
What goes wrong: A list verified 6 months ago is now 10-20% stale. Bouncing on those drives spam folder placement. Future sends to valid contacts also go to spam.
How to avoid: Quarterly re-verification of active outreach lists. Annual for transactional CRM lists.
Ignoring Unknown results
What goes wrong: You treat Unknown as 'probably valid.' Half of Unknowns are actually invalid. Bounce rate spikes.
How to avoid: Re-verify Unknowns in 30 min. If still Unknown, skip — better to lose a possible-good than to send 50 likely-bounces.
Single-email verifying lists you should bulk-verify
What goes wrong: You verify 200 emails one at a time. 4 hours of work that Bulks would do in 5 minutes.
How to avoid: Above 10-20 emails, always Bulks → Email Verifier.
Verifying right before sending instead of during list-building
What goes wrong: You verify a 5,000-email list 10 minutes before launch. Wait 1 hour for completion. Realize 30% are invalid. Launch delayed.
How to avoid: Verify during list-building, not at launch. Build clean lists, not lists-to-be-cleaned.
Recap
Valid = the specific mailbox exists. Accept-all = the server accepts mail for any address, but we cannot confirm the specific mailbox. Accept-all looks fine to send but emails may go to a black hole.
For warm audiences (existing customers, opt-ins, replied prospects) — usually yes. For cold outreach — never. Use Hunter's domain pattern check to gauge legitimacy of an Accept-all server.
~100-200 emails per minute. A 1,000-list takes 10-15 min. A 10K-list takes ~1-2 hours.
Yes. A verified email today may be invalid in 3 months if the person leaves their job. Re-verify quarterly for active campaigns.
Roughly equivalent on accuracy (95-97% agreement on Valid/Invalid). For maximum confidence on $100K+ campaigns, use two services and only send to addresses both call Valid.
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