MailboxValidator Free Email Checker
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For Agents
Check whether a single email address belongs to a free webmail provider - useful for filtering personal addresses out of B2B lead routing.
Use for: Check whether jane@gmail.com is a free email provider, Find which signups in the last 24 hours used personal email domains, Get the free-provider flag for a B2B lead before routing it to sales, List all CRM contacts whose email domain is a free webmail service
Not supported: Does not detect disposable addresses, verify SMTP existence, or send email - use for free-provider detection only.
MailboxValidator Free Email Checker is a single-purpose endpoint that determines whether an email address comes from a free email provider (gmail.com, yahoo.com, outlook.com and similar). The API returns a JSON or XML response indicating the free-provider verdict for one email at a time and is typically used as a lead-quality signal in CRM pipelines. The OpenAPI spec exposes one operation: GET /v1/email/free.
Install Jentic One Beta
Connect the MailboxValidator Free Email Checker to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the MailboxValidator Free Email Checker, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fmailboxvalidator.com%2Fmailboxvalidator-checker" | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fmailboxvalidator.com%2Fmailboxvalidator-checker" | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with MailboxValidator Free Email Checker API.
Classify an email address as free-provider or business via a single GET
Return JSON or XML output controlled by a format query parameter
Distinguish gmail, yahoo, hotmail, outlook and similar consumer domains
Support a credit-based usage model with a per-key API key parameter
Use Cases
Patterns agents use MailboxValidator Free Email Checker API for, with concrete tasks.
★ B2B Lead Quality Filter
Filter out free webmail addresses from inbound lead forms so sales reps focus on prospects with corporate domains. The Free Email Checker returns a simple boolean-style verdict per address, which can be wired into a Marketo or HubSpot workflow as a routing condition. A typical setup adds the free-provider flag to the lead record at create time.
For each new HubSpot contact, call GET /v1/email/free?email={email}&key={key} and write the is_free boolean to a custom property.
Trial Abuse Reduction
Reduce trial abuse by flagging or limiting accounts created with free webmail providers. Combined with a disposable-email check, the free-provider flag is a strong signal that a signup will not convert to a paid customer. This is a single GET per signup and adds negligible latency.
Call /v1/email/free for trial@gmail.com and if is_free is true, gate the trial behind manual review.
Agent-Driven Lead Scoring
An AI agent that scores incoming leads can call the Free Email Checker through Jentic to add an is_free signal to its scoring vector. Combined with company enrichment, the agent can autonomously route corporate leads to AEs and free-mail leads to a self-serve nurture track without human intervention.
Run /v1/email/free on a batch of 200 lead emails and tag each lead in Salesforce with a free_email custom field for routing rules.
Key Endpoints
1 endpoints — mailboxvalidator free email checker is a single-purpose endpoint that determines whether an email address comes from a free email provider (gmail.
METHOD
PATH
DESCRIPTION
GET
/v1/email/free
Check whether an email address is from a free email provider
GET
/v1/email/free
Check whether an email address is from a free email provider
Why Jentic?
What agents get from Jentic-routed access to this vendor.
Setup
Wiring the MailboxValidator Free Email Checker by hand means attaching your API key to each request, targeting the api.mailboxvalidator.com host, and reading the free-provider result yourself. Through Jentic you install once, import the checker from the API Directory, store the key once, and your agent calls it.
Permission scoping
This API offers a single free-provider check with the address carried in the request, so limit the agent to the operation it needs, the free-email lookup, and nothing more. The operation set is your choice.
Credential isolation
Your MailboxValidator API key is stored once, encrypted, by your own Jentic One instance and injected at execution time. It never enters the agent's prompt, logs, or context.
Intent-based discovery
Agents search Jentic by intent such as 'is this a free email provider', and Jentic returns the matching MailboxValidator operation with its input schema so the agent calls the right endpoint without browsing the reference docs.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using MailboxValidator Free Email Checker API through Jentic.
What authentication does the Free Email Checker use?
The endpoint takes an API key passed as the key query parameter alongside the email being checked. The OpenAPI spec does not declare a securityScheme component; the key is documented at https://www.mailboxvalidator.com/api-email-freem. Through Jentic the key is stored encrypted and injected at execution time.
Can I get JSON or XML back from this endpoint?
Yes. GET /v1/email/free accepts a format query parameter that selects either JSON or XML output. JSON is the default and the recommended choice for agent and SDK consumers.
What are the rate limits for the Free Email Checker?
MailboxValidator uses a credit model rather than a fixed per-second rate limit. Each call against /v1/email/free consumes credits from your subscription, and the free tier provides a fixed monthly allowance. The OpenAPI spec does not encode a per-second throttle.
How do I check whether an email is free through Jentic?
Search Jentic for "check free email provider" to load the GET /v1/email/free operation, then execute with email and key parameters. The response is a JSON object whose is_free field is the verdict you want.
Is the Free Email Checker available on a free plan?
Yes. MailboxValidator publishes a free tier with a monthly credit allowance for the Free Email Checker. Paid tiers raise the credit cap and unlock other MailboxValidator products such as the disposable checker and full single-validation API.
Can I limit what my agent is allowed to do with the MailboxValidator Free Email Checker?
Yes. Because you run Jentic One yourself, your own rules decide which operations and credentials the agent may use. This API exposes only the single free-provider lookup, GET /v1/email/free, so you can grant the agent that one operation and nothing else. Your MailboxValidator API key stays with your instance and is injected at execution time, so the agent can run the free-email check without ever seeing the key.
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