You have an email address. You need to know who it belongs to: their name, job title, company, seniority, phone number. Maybe you need to verify that the person is who they claim to be. Maybe you need to fill in a sparse CRM record so your sales team has something to work with.
Reverse email lookup is the process of taking an email address as input and returning a full person profile as output. It's one of the most common operations in B2B data, and it's the core function behind person enrichment APIs.
This article covers how reverse email lookup actually works under the hood, where B2B lookup differs from the consumer people-search tools you've seen before, and how to build it into your systems.
How It Works
Reverse email lookup sounds simple (email in, profile out) but the underlying process involves several steps.
Domain Extraction and Resolution
The lookup starts with the email domain. jane@acmecorp.com tells you the person likely works at Acme Corp. The system resolves the domain to a company record via company enrichment: company name, employee count, industry, company size, growth trends. This firmographic context helps qualify the lead at the account level before you even look at the individual.
For personal email domains like Gmail or Outlook, the domain alone isn't useful. The system relies more heavily on the other steps below.
Identity Matching
The email address is matched against a database of person records. This isn't just string matching. The system checks for exact matches first, then looks at aliases, historical email addresses, and cross-references with other identifiers (name, phone, LinkedIn URL) to find the right person.
Good identity resolution handles common complications: people with multiple email addresses, shared inboxes (like sales@company.com which won't resolve to a single person), and email addresses that have been recycled after someone left a company.
Profile Assembly
Once the person is identified, the system assembles a full profile from available data sources: current job title, seniority level, job function, company details, location, phone numbers, social profiles, work history, and education. Each field has its own confidence score based on how recently it was confirmed and how many sources agree.
Validation
Before returning the profile, the system runs checks. Is the email address still deliverable? Does the person still work at the company associated with the email? Has the job title been confirmed recently? Fields that can't be validated are either returned with lower confidence scores or excluded.
The whole process takes under a second for API-based lookups.
B2B Lookup vs. Consumer People Search
If you've ever Googled "reverse email lookup," you've seen tools like Spokeo, BeenVerified, and ThatsThem. These are consumer people-search tools. They solve a different problem than B2B enrichment APIs.
The data scope is the biggest difference. Consumer tools focus on personal information: home address, age, relatives, court records, social media profiles. B2B APIs focus on professional information: job title, company, seniority level, work email, direct phone, company firmographics.
The sources differ too. Consumer tools often aggregate public records, social media, and data broker lists. B2B APIs draw from commercially licensed databases, business registrations, verified corporate directories, and professional data partnerships. The sourcing matters for both accuracy and compliance.
Consumer tools are typically web-based with manual lookups. B2B APIs are designed for programmatic access: RESTful endpoints, JSON responses, webhook integrations, batch processing. They're built to be wired into CRMs, enrichment pipelines, and scoring models.
B2B APIs also return confidence scores per field, so you can make decisions about which data to trust and which to verify. A phone number with "high" confidence is worth dialing. One with "low" confidence might need manual verification first. Consumer tools just return whatever they find.
Then there's compliance. B2B enrichment providers (reputable ones, at least) maintain opt-out infrastructure, process CCPA deletion requests, and track data provenance. Consumer people-search sites have a mixed record on this.
Use Cases
Signup and Form Enrichment
The most common use case. A lead fills out a form with their email and maybe their name. You need the rest.
A reverse email lookup at the point of form submission fills in job title, company, seniority, phone, and location before the record hits your CRM. Your sales team sees a complete profile within seconds instead of a bare email address.
This is the pattern covered in detail in Building a Real-Time Enrichment Pipeline with a Person API. The enrichment API call is the same. The input is the email from the form. The output is a full profile.
import os
import requests
response = requests.post(
"https://api.datalegion.ai/person/enrich",
headers={"API-Key": os.environ["DATALEGION_API_KEY"]},
json={"email": form_submission["email"]},
)
data = response.json()
person = data["matches"][0]["person"] if data.get("matches") else None
# Now you have: first_name, last_name, job_title, seniority_level,
# company_name, company_size, mobile_phone, work_email, linkedin_url...The reduction in form fields is a side benefit. Instead of asking for title, company, and phone on the form (which increases abandonment), you ask for email only and let enrichment fill in the rest.
CRM Data Hygiene
Your CRM has thousands of records that were imported months or years ago. Job titles are outdated. People have changed companies. Emails bounce. Phone numbers are disconnected.
A batch reverse email lookup re-enriches these records. Send the email addresses through the API, compare the returned profiles against what's in the CRM, and update the fields that have changed.
This works well as a recurring job. Run it monthly or quarterly against records that haven't been enriched recently. Track how many records changed on each run. A high change rate tells you the CRM is decaying fast and you may need to run hygiene more frequently.
Fraud Detection and Identity Verification
When someone signs up for your product or submits a request, you want to verify they are who they claim to be. Reverse email lookup provides a fast first layer of verification.
Does the email domain match the company they claimed? Does the job title match the role they say they have? Is the email address associated with a real professional profile, or is it a throwaway?
This isn't a replacement for full identity verification (KYC/KBA), but it's a lightweight check that catches the obvious mismatches. A signup claiming to be a "VP of Engineering at Google" with a Gmail address and no matching professional profile is worth flagging.
Lead Scoring
The fields returned by reverse email lookup are the inputs to lead scoring. Seniority level, company size, industry, and job function are the fields that matter most for B2B scoring models. Many teams enrich at both the person and company level. Person enrichment provides contact attributes (seniority, title, job function), while company enrichment provides firmographic signals (employee count, growth trajectory, workforce distributions) that feed into account-based scoring.
Without enrichment, your scoring model only has whatever the lead provided on the form. With enrichment, you can score accurately from the first interaction.
Email Verification (as a Side Effect)
Reverse email lookup isn't the same as email verification, but it overlaps. If the API returns a match with a validated email field, you know the address is associated with a real person and is likely deliverable. If the API returns no match, the email may still be valid (the person just isn't in the database), but it's a signal worth noting.
Some teams use the match/no-match as a lightweight quality filter. Leads that enrich successfully get fast-tracked. Leads that don't match get routed to a manual review queue.
API Integration
A basic integration takes about 30 minutes. The core is a single POST request.
Request:
curl -X POST "https://api.datalegion.ai/person/enrich" \
-H "Content-Type: application/json" \
-H "API-Key: YOUR_API_KEY" \
-d '{"email": "mchen@growthanalytics.io"}'Response (abbreviated):
{
"matches": [
{
"person": {
"full_name": "michael james chen",
"first_name": "michael",
"last_name": "chen",
"job_title": "director of engineering",
"company_name": "growth analytics inc",
"company_domain": "growthanalytics.io",
"company_industry": "technology, information and internet",
"company_size": "201-500",
"seniority_level": "director",
"job_function": "engineering",
"city": "austin",
"state": "texas",
"work_email": "mchen@growthanalytics.io",
"mobile_phone": "+15559876543",
"emails": [
{
"address": "mchen@growthanalytics.io",
"type": "professional",
"current": true,
"validated": true,
"confidence": "high"
}
],
"phones": [
{
"type": "mobile",
"number": "+15559876543",
"current": true,
"confidence": "high"
}
]
},
"match_metadata": {
"matched_on": ["email"],
"match_type": "exact",
"match_confidence": "high"
}
}
],
"total": 1
}You send an email. You get back a full professional profile with confidence scores on each field. No match returns a 404.
For production use, add retry logic for rate limits (HTTP 429) and cache results to avoid duplicate lookups when the same email comes through multiple systems. The enrichment pipeline tutorial covers both patterns with code examples.
What to Look For in a Provider
If you're evaluating reverse email lookup APIs, the questions that matter are:
Match rate is first, and you need to test it on your data, not theirs. Request a trial and run a sample of real emails from your CRM.
Field completeness matters just as much. A match that only returns name and company isn't very useful. Check how often critical fields (job title, seniority, phone, company size) are populated on matched records.
Ask about freshness. How recently was the data confirmed? A record last confirmed six months ago may have a job title that no longer applies. Look for providers that expose last_confirmed timestamps.
And if you're enriching inline, speed counts. The API needs to respond in under 500ms. Test latency from your infrastructure, not from their status page.
Reverse email lookup is one of those capabilities that's easy to underestimate. It looks simple. Email in, data out. But the quality of that output (freshness, completeness, response speed) determines whether your downstream workflows actually work. Pick the provider carefully.