Guide

How to Verify B2B Email Leads Before You Hit Send

A step-by-step method to verify B2B email leads (syntax, MX, mailbox, catch-all, role freshness) so your cold emails land and your sending domain stays healthy.

Published 30 September 2026

A list of 1,000 contacts is only worth the ones that reach a real person in the right job. Sending to bad addresses doesn’t just waste effort. High bounce rates tell inbox providers you’re a careless sender, and your good emails start landing in spam too.

Here’s the verification method we use, laid out so you can apply it to any list, including one you bought somewhere else.

Step 1: Syntax check

Throw out anything that isn’t a valid address: missing @, spaces, illegal characters, obvious typos like gmial.com. This is the cheapest check and catches data-entry junk.

Step 2: Domain and MX records

Check that the domain exists and has MX records, meaning it’s set up to receive email. Parked domains, dead startups and misspelled domains fail here.

Step 3: Mailbox (SMTP) check

The verifier connects to the company’s mail server and asks, in effect, “would you accept mail for this address?”, then disconnects before sending anything. There are three possible results:

• Valid: the server confirmed the mailbox exists.
• Invalid: the server rejected it. Remove it.
• Unknown: the server didn’t give a clear answer. Treat these as risky.

Step 4: Catch-all detection

Some companies set their domain to accept mail for any address. The mailbox check says “valid” for everything, including made-up names, so it tells you nothing.

Good verification detects catch-all domains and labels them separately rather than counting them as confirmed. If you send to catch-alls, send them in smaller batches and watch bounces closely.

Step 5: Role-based and disposable addresses

Addresses like info@, sales@ or hr@ reach a shared inbox, not a decision-maker, and often generate spam complaints. Disposable-domain addresses are worthless for B2B. Flag or remove both.

Step 6: Is the person still there?

An email can pass every technical check and still belong to someone who changed jobs last quarter. Cross-check the current title and employer against their public LinkedIn profile or the company’s team page. This is the step automated tools skip, and it’s why “verified” lists still produce replies like “I left in March.”

Step 7: De-duplicate and suppress

Remove duplicates, anyone who has previously opted out of your emails, and existing customers. Keep a suppression list and check every new list against it.

Healthy sending habits

Verification keeps your list clean. These habits keep your domain healthy:

• Authenticate your domain. Set up SPF, DKIM and DMARC. Gmail and Yahoo require authentication from bulk senders.
• Watch your numbers. Keep hard bounces low (many teams aim for under ~2%) and spam complaints very low. Google asks bulk senders to stay below a 0.3% spam rate.
• Use a secondary sending domain for cold outreach so your main domain is protected.
• Ramp up slowly. New inboxes should start with a small daily volume and build up over a few weeks.
• Make opting out easy, and honour it right away.

A 25-lead test for any vendor

Before you commit to any lead provider:

1. Ask for 25 sample records in your exact target segment.
2. Run them through Steps 1–6 yourself. A free verifier tier plus LinkedIn is enough.
3. Score them: how many are the right role, at a real company, with a mailbox that validates?

If a vendor won’t give you a sample, that tells you something. We’ll send you 25 free records built to your spec.