B2B Data Vendors: How to Verify Emails and Phone Numbers Before You Deliver a List

Why "verified at collection" isn't enough

Whether you scrape, enrich, buy and resell, or build custom lists by hand, your data has an age. People change jobs, companies change domains, mailboxes get closed when someone leaves. A record that was valid when it entered your database tells you about that day.

Your buyer, meanwhile, is going to load the file into a sequencer and send within days. If a chunk bounces, they don't blame decay. They blame you, ask for a refund or credits, and don't come back. Buyers increasingly ask vendors about this up front; see questions to ask a B2B data vendor and lead database email accuracy claims for the buyer's side.

The delivery checklist

1. Verify the order, not the database

Pull the rows for this order and verify those, today. It's cheaper than re-checking millions of rows you won't ship this week, and the result is as fresh as it can be. Upload the file to the verify page or run it through the API in your delivery pipeline. Files can be up to 100,000 rows per upload.

2. Label emails honestly

SimpleVerifier returns each address as valid, invalid, risky or unknown, with a reason. A delivery format that holds up:

Your label	What it contains
Verified	Mail server accepted the mailbox on the date shown
Risky: catch-all	Domain accepts all mail; likelihood grade higher, medium or lower
Risky: other	Role address, full inbox, or similar, with the reason
Not included	Invalid, disposable, or no usable answer

Don't merge risky into verified. A catch-all server accepts any address, so nothing can confirm the person, and SimpleVerifier reports catch-alls as risky, never guessed valid (how the likelihood grade works). In B2B lists catch-alls can be a large share of rows, because many company mail setups accept everything. If you sell them, sell them as a tier the buyer can choose. See UpLead's valid-only vs accept-all for how one vendor exposes the choice.

3. Put the date on every row

Add a verified_at column. It costs nothing and answers the question careful buyers ask first. It also protects you: a complaint about bounces three months after delivery is a decay conversation, not a quality one.

4. Deliver phones in a usable shape

Phone data causes as many complaints as email, mostly because of format and type confusion:

• E.164 for every number. +442079460958, not 020 7946 0958 or a number Excel turned into 4.42079E+11. The phone number formatter and bulk phone number validator do it in bulk.
• Drop numbers that can't exist. A numbering-plan check removes wrong lengths and unallocated ranges.
• Drop placeholders. Scraped and form-sourced data picks up 555-555-5555, 0000000000 and fictional ranges. The fake phone number checker flags them.
• Say what the number is. Mobile, direct dial or company switchboard. Buyers who expect a person and reach reception file a complaint. One column per type beats one "phone" column.
• Line type where it matters. For US and Canadian mobiles, a live carrier lookup returns the carrier-reported line type (mobile, landline, VoIP). Buyers running SMS need it. See VoIP numbers in lead lists.

5. Dedupe and normalise

Dedupe on lower-cased email and on E.164 phone, and cap contacts per company if the order asks for it. Useful tools: remove duplicate emails, remove duplicate phone numbers, limit contacts per company, job title normalizer and company name cleaner.

6. Ship a summary with the file

A short cover sheet with counts per label, the verification date and what each label means saves you a support thread. Agencies on SimpleVerifier's Agency plan can produce branded client reports; others can export the CSV summary.

Handling refund and replacement requests

Even a well-verified list will have some bounces after delivery, because mailboxes close every week. A clear policy saves arguments:

• Define the window. For example, bounces reported within a set number of days of delivery get replacement records.
• Ask for the bounce messages. A hard bounce such as "550 5.1.1 user unknown" is a dead mailbox; a soft bounce or a policy block is not a data problem. See hard bounce vs soft bounce.
• Exclude risky rows from guarantees if you labelled them risky at delivery. That's the point of labelling them.

Compliance belongs to the buyer, but help them

You don't decide how the buyer contacts people, but you can make the legal checks easier: include country per row, mark EU, UK and Canadian contacts, and keep source information. Point buyers to the free GDPR email consent checker and CASL consent checker. For phone outreach in the US, mobiles vs landlines matter under the TCPA; see TCPA: mobile vs landline. This isn't legal advice.

If buyers will send at volume from a new dedicated IP, the IP warmup schedule calculator is worth linking in your delivery notes. A verified list and a proper warmup are what keep the first week from going wrong.

Automating it

Most vendors end up with a pipeline: query → export → verify → label → deliver. The API checks addresses one at a time; bulk files can go through the upload. If your team works with AI assistants, the MCP server lets an assistant verify a sample before a rep sends it to a prospect as a preview. See bulk verify a CSV with the API.

What it costs

• Free: 100 checks with a Google sign-in, no card. Try it on a sample order.
• Starter, $9 a month: 2,500 emails a month.
• Pro, $39 a month: Unlimited email verification*, phone format checks, the email finder, the API and the MCP server.
• Business and Agency plans add seats, a priority lane and more API calls; see pricing.
• Pro + Phone, $49.99 a month: adds 5,000 live carrier lookups a month.

*Fair use: the first 100,000 checks a month at full speed, then slower, never cut off. API calls and phone lookups are counted separately.

More reading: test a new lead source, lead list quality check, lead data bounce credit refunds, white-label email verification for agencies.