Email Validation

Overview

The Email Validation API helps you verify email addresses before sending, reducing bounces and protecting your sender reputation.

Validate emails at the point of collection (signup forms, checkout) to prevent invalid addresses from entering your database.

Validation Checks

Syntax

RFC 5322 compliant format validation

MX Records

Domain has valid mail servers

Disposable

Temporary/throwaway email detection

Role-based

Generic addresses (info@, support@)

Free Provider

Gmail, Yahoo, Outlook detection

Catch-all

Domain accepts any address

Quality Score

Each email receives a quality score from 0-100:

Score	Rating	Description
80-100	Excellent	Safe to send, high deliverability
60-79	Good	Likely valid, minor risks
40-59	Risky	May bounce or be problematic
0-39	Poor	High risk, likely invalid

Single Validation

POST/v1/validate/email

Validate a single email address with comprehensive checks.

Request Body

string

required

Email address to validate

check_smtp

boolean

default:"false"

Perform SMTP mailbox verification (slower but more accurate)

check_catch_all

boolean

default:"false"

Check if domain is a catch-all (accepts any address)

cURL

curl -X POST https://www.unosend.co/api/v1/validate/email \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "john@example.com",
    "check_catch_all": true
  }'

Response

200 OK

{
  "email": "john@example.com",
  "valid": true,
  "score": 85,
  "reason": null,
  "checks": {
    "syntax": true,
    "mx_records": true,
    "disposable": false,
    "role_based": false,
    "free_provider": false,
    "catch_all": false,
    "smtp_valid": null
  },
  "details": {
    "local_part": "john",
    "domain": "example.com",
    "mx_hosts": ["mail.example.com", "mail2.example.com"],
    "suggestion": null
  }
}

Bulk Validation

POST/v1/validate/emailsPRO

Validate multiple email addresses in a single request (up to 1,000 emails synchronously).

For validating more than 1,000 emails, use the Async Bulk Validation endpoint which supports up to 500,000 emails.

Request Body

emails

array

required

Array of email addresses to validate (up to 1,000,000 on Pro/Scale/Enterprise plans)

check_smtp

boolean

default:"false"

Perform SMTP mailbox verification

check_catch_all

boolean

default:"false"

Check for catch-all domains

cURL

curl -X POST https://www.unosend.co/api/v1/validate/emails \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": [
      "valid@company.com",
      "invalid@nonexistent.xyz",
      "temp@mailinator.com"
    ]
  }'

Response

200 OK

{
  "total": 3,
  "valid": 1,
  "invalid": 1,
  "risky": 1,
  "summary": {
    "deliverable": 1,
    "undeliverable": 1,
    "risky": 1,
    "unknown": 0
  },
  "results": [
    {
      "email": "valid@company.com",
      "valid": true,
      "score": 90,
      "reason": null,
      "checks": {
        "syntax": true,
        "mx_records": true,
        "disposable": false,
        "role_based": false,
        "free_provider": false,
        "catch_all": null,
        "smtp_valid": null
      },
      "details": {
        "local_part": "valid",
        "domain": "company.com"
      }
    },
    {
      "email": "invalid@nonexistent.xyz",
      "valid": false,
      "score": 25,
      "reason": "Domain has no mail server (MX records)",
      "checks": {
        "syntax": true,
        "mx_records": false,
        "disposable": false,
        "role_based": false,
        "free_provider": false,
        "catch_all": null,
        "smtp_valid": null
      },
      "details": {
        "local_part": "invalid",
        "domain": "nonexistent.xyz"
      }
    },
    {
      "email": "temp@mailinator.com",
      "valid": false,
      "score": 40,
      "reason": "Disposable email address",
      "checks": {
        "syntax": true,
        "mx_records": true,
        "disposable": true,
        "role_based": false,
        "free_provider": false,
        "catch_all": null,
        "smtp_valid": null
      },
      "details": {
        "local_part": "temp",
        "domain": "mailinator.com"
      }
    }
  ]
}

Async Bulk Validation

POST/v1/validate/bulkPRO

Validate large email lists asynchronously (up to 500,000 emails). Perfect for cleaning your audience lists before sending campaigns.

This endpoint starts a validation job that runs in the background. Use the job ID to check progress and retrieve results.

Pricing

Plan	Credits	Price
Free	1,000	$0
Pro	100,000	$29

Request Body

emails

array

Array of email addresses to validate (up to 500,000)

audience_id

string

Alternatively, validate all contacts in an audience

cURL

curl -X POST https://www.unosend.co/api/v1/validate/bulk \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "emails": ["user1@example.com", "user2@test.com", ...]
  }'

Or validate an entire audience:

cURL

curl -X POST https://www.unosend.co/api/v1/validate/bulk \
  -H "Authorization: Bearer un_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "audience_id": "aud_abc123"
  }'

Response

200 OK

{
  "data": {
    "job_id": "val_abc123xyz",
    "status": "pending",
    "total": 10000,
    "credits_used": 10000,
    "credits_remaining": 90000,
    "estimated_time_minutes": 17,
    "message": "Validation job started for 10,000 emails."
  }
}

Check Validation Progress

GET/v1/validate/bulk/:job_id

Check the progress of an async validation job.

cURL

curl https://www.unosend.co/api/v1/validate/bulk/val_abc123xyz \
  -H "Authorization: Bearer un_your_api_key"

Response

200 OK

{
  "data": {
    "job_id": "val_abc123xyz",
    "status": "processing",
    "total_emails": 10000,
    "valid_count": 4500,
    "invalid_count": 500,
    "progress_percent": 50
  }
}

Status Values

Status	Description
`pending`	Job is queued, waiting to start
`processing`	Validation in progress
`completed`	All emails validated
`failed`	Job failed (check error message)
`cancelled`	Job was cancelled

Get Validation Results

GET/v1/validate/bulk/:job_id/results

Retrieve the results of a completed validation job.

cURL

curl https://www.unosend.co/api/v1/validate/bulk/val_abc123xyz/results \
  -H "Authorization: Bearer un_your_api_key"

Response

200 OK

{
  "data": {
    "job_id": "val_abc123xyz",
    "valid_count": 9200,
    "invalid_count": 800,
    "invalid_emails": [
      { "email": "test@tempmail.com", "reason": "disposable" },
      { "email": "bad@gmial.com", "reason": "typo" },
      { "email": "fake@noexist.xyz", "reason": "no_mx" },
      { "email": "bounce@invalid.com", "reason": "invalid_mailbox" },
      { "email": "info@company.com", "reason": "role_based" }
    ]
  }
}

Reason Codes

Reason	Description
`syntax`	Invalid email format
`disposable`	Temporary/throwaway email domain
`typo`	Common domain typo detected
`no_mx`	Domain has no mail servers
`invalid_mailbox`	Mailbox doesn’t exist (SMTP check failed)
`role_based`	Generic address (info@, support@, etc.)

Cancel Validation Job

DELETE/v1/validate/bulk/:job_id

Cancel a running validation job.

cURL

curl -X DELETE https://www.unosend.co/api/v1/validate/bulk/val_abc123xyz \
  -H "Authorization: Bearer un_your_api_key"

Response

200 OK

{
  "message": "Validation job cancelled",
  "job_id": "val_abc123xyz",
  "status": "cancelled"
}

Processing Time

Async bulk validation processes approximately 10 emails per second:

Emails	Estimated Time
1,000	~2 minutes
10,000	~17 minutes
100,000	~2.8 hours
500,000	~14 hours

Check Types Explained

Syntax Check

Validates email format according to RFC 5322:

Proper local@domain.tld format
No invalid characters
Length limits (64 chars local, 254 total)
No consecutive dots

MX Records Check

Verifies the domain has configured mail servers:

DNS lookup for MX records
Returns list of mail hosts
No MX = domain can’t receive email

Disposable Detection

Identifies temporary/throwaway email services:

10minutemail, Mailinator, Guerrilla Mail
100+ disposable domains tracked
High bounce risk

Role-based Detection

Flags generic/group addresses:

info@, support@, sales@, admin@
Often shared mailboxes
Higher complaint risk

Free Provider Detection

Identifies free email services:

Gmail, Yahoo, Hotmail, Outlook
Not necessarily bad, just informational

Catch-all Detection

Checks if domain accepts all emails:

Tests random address acceptance
Catch-all domains can’t verify individual addresses
Higher risk of invalid addresses

SMTP Verification

Direct mailbox existence check:

Connects to mail server
Tests if address is accepted
Most accurate but slower

Typo Detection

The API automatically detects common typos and suggests corrections:

{
  "email": "john@gmial.com",
  "valid": false,
  "details": {
    "domain": "gmial.com",
    "suggestion": "john@gmail.com"
  }
}

Common typos detected:

gmial.com → gmail.com
hotmal.com → hotmail.com
yaho.com → yahoo.com
outlok.com → outlook.com

Best Practices

Validate at collection

Check emails when users sign up or enter their address, not just before sending.

Use appropriate checks

Signups: Full validation with catch-all detection
Transactional: Quick syntax + MX check
Marketing lists: Bulk validation with SMTP

Handle low scores gracefully

Don’t reject users immediately. Ask them to confirm or re-enter their email.

Respect rate limits

Bulk validation counts against your API rate limits. Process large lists in batches.

API Reference

Emails

Inbound

Domains

API Keys

Audiences

Contacts

Broadcasts

Webhooks

Templates

​Overview

​Validation Checks

Syntax

MX Records

Disposable

Role-based

Free Provider

Catch-all

​Quality Score

​Single Validation

​Request Body

​Response

​Bulk Validation

​Request Body

​Response

​Async Bulk Validation

​Pricing

​Request Body

​Response

​Check Validation Progress

​Response

​Status Values

​Get Validation Results

​Response

​Reason Codes

​Cancel Validation Job

​Response

​Processing Time

​Check Types Explained

​Syntax Check

​MX Records Check

​Disposable Detection

​Role-based Detection

​Free Provider Detection

​Catch-all Detection

​SMTP Verification

​Typo Detection

​Best Practices

Overview

Validation Checks

Quality Score

Single Validation

Request Body

Response

Bulk Validation

Request Body

Response

Async Bulk Validation

Pricing

Request Body

Response

Check Validation Progress

Response

Status Values

Get Validation Results

Response

Reason Codes

Cancel Validation Job

Response

Processing Time

Check Types Explained

Syntax Check

MX Records Check

Disposable Detection

Role-based Detection

Free Provider Detection

Catch-all Detection

SMTP Verification

Typo Detection

Best Practices