How to Verify ContactOut Emails Before You Send (Work and Personal)

To verify ContactOut emails, get them into a CSV, split work addresses from personal ones, and run the whole file through an email verifier right before you send. ContactOut returns both work and personal emails, so one file usually mixes company domains with Gmail, Outlook and Yahoo addresses, and those behave differently. Send to the valid rows, hold the risky ones (catch-all company domains and Yahoo-hosted inboxes) for a slower campaign, and suppress the invalid ones. You can check a sample free at /verify.

Split work and personal emails first →

Why ContactOut files need a second check

ContactOut's homepage lists work emails, personal emails and direct dials in its data, and says it is used by recruiters and sales reps. Its FAQ says it returns verified work and personal emails.

A second check before sending is still worth it, for reasons that have nothing to do with the data source:

• Time. You may have saved the contact weeks ago. A work address stops working when the person leaves.
• Company changes. A company that moves to a new email provider or merges with another can retire old addresses.
• Catch-all domains. Some company mail servers accept every address at first and bounce later. No mailbox check can confirm a single address there.
• Hand edits. Rows copied by hand pick up typos and stray spaces.
• Mixed sources. If you combine ContactOut contacts with leads from other tools, one bad source can raise the bounce rate for all of them.

A bounce rate above a few percent can get a sequence paused or a sending domain flagged. Our bounce rate thresholds by platform guide lists the limits sequencers publish.

Step 1: Get the contacts into one CSV

Use whatever route your ContactOut plan gives you: an export, a sync to your CRM or ATS, or the API. The goal is one file with at least these columns:

• First name, last name
• Company
• Work email
• Personal email
• Source (add "ContactOut" yourself if it isn't there)

If one row has several emails in one cell, split them with split multiple emails in a cell. If you have both a work and a personal email for one person, keep them in separate columns; don't merge them into one.

Then remove duplicates with the duplicate email remover. Lists built from the extension over several weeks often contain the same person twice.

Step 2: Split work emails from personal emails

Run the email column through the free vs business email filter. It sorts addresses at gmail.com, outlook.com, yahoo.com and similar into one group, and company domains into another.

Why split them?

Group	Typical use	What to watch
Work emails	B2B sales, partnerships	Catch-all company domains; job changes
Personal emails	Recruiting, candidate outreach	Yahoo-hosted inboxes can't be confirmed; personal inboxes are stricter about spam

The message is often different too. A recruiter reaching a candidate at a personal address writes a different email from a sales rep pitching a company. Our guide on personal emails in a B2B lead list covers when to keep them.

You can also see who hosts each address with the bulk email provider lookup. That tells you which company domains run on Google Workspace or Microsoft 365, which matters for deliverability.

Step 3: Verify the file

Upload the CSV at /verify. The verifier checks syntax, the domain's mail server and, where the server allows it, the mailbox itself, without sending an email.

You get three groups back:

Result	What it means	What to do
Valid	The mail server confirmed the mailbox	Send
Risky	Reachable but not confirmable: catch-all domain, Yahoo-hosted inbox, full mailbox	Hold for a smaller, slower campaign
Invalid	Rejected, no mail server, or broken syntax	Suppress; never send

Step 4: Handle the risky group

Most risky results in a ContactOut file fall into two groups.

Catch-all company domains. The company's mail server says yes to every address, real or not. You can check a list of domains with the bulk catch-all checker. For these:

• Send in small batches from your most established inbox.
• Watch bounces after the first batch. If they are high, stop.
• Our what is a catch-all domain guide explains the trade-off.

Yahoo-hosted personal inboxes. yahoo.com and aol.com, plus ISP domains like att.net and sbcglobal.net, accepted a made-up address in our mailbox provider study. That means no verifier can confirm them. They aren't necessarily bad; they are just unknown. Send to them after your valid group and watch for bounces.

Step 5: Upload to your sequencer or ATS

1. Upload only the valid rows to your main campaign.
2. Put the risky rows in a separate, slower campaign, or hold them.
3. Add the invalid rows to your suppression list so nobody re-imports them. The suppression list merger combines them with bounces and unsubscribes from other tools.
4. If your sequencer needs specific column names, clean CSV columns before import shows how to map them.

When to re-verify

• Right before every campaign that uses contacts saved more than a few weeks ago.
• After a long pause. A candidate pipeline you built last quarter has had time to decay. The email list decay calculator gives a rough estimate.
• After a bounce spike. If one campaign bounces more than usual, re-check the rest of that list before sending again.

A quick worked example (illustrative)

A recruiting team saves 2,000 candidates from ContactOut over a month. Each row has a personal email, and many also have a work email.

1. They export, dedupe and split. Most candidates have a personal address; they decide to write only to those, since they are recruiting.
2. The personal file is verified. The Gmail and Outlook addresses come back mostly valid. The Yahoo and AT&T addresses come back risky, as expected.
3. Invalid rows go to suppression.
4. The valid rows go into the main campaign. The risky rows go into a second campaign that sends slower.

The numbers here are made up to show the steps, not real results.

Common mistakes

• Verifying once, sending months later. A check is a snapshot. Verify again right before the campaign.
• Merging work and personal emails into one column. You lose the choice of which one to write to, and your sequencer may email both.
• Treating risky as invalid. Deleting every catch-all and Yahoo address throws away real people. Send to them separately instead.
• Treating risky as valid. Putting them in the main campaign is how bounce rates jump on day one.
• Forgetting suppressions. If a candidate asked you to stop, a new export from any tool can bring them back. Check every new file against your suppression list first.
• Skipping the source column. When a campaign bounces, you want to know which tool the bad rows came from.

Legal basics

Verifying an address is not consent to email it. Follow the rules where the recipient lives. Our guides cover CAN-SPAM, GDPR for B2B cold email and CASL in Canada. In some places the rules for personal addresses are stricter than for work ones; the UK's PECR, for example, treats individual subscribers differently from corporate ones. Our PECR guide explains the difference.

Verify your ContactOut file

Upload a sample at /verify. The first 100 checks are free with a Google sign-in, no card.

Pro, $39 a month: Unlimited email verification.* Never metered, never cut off. See pricing.

*Fair use: the first 100,000 checks a month at full speed, then slower, never cut off.

More: why cold emails bounce, clean a Lusha or Seamless export, email verification statuses explained.