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Email Validation

Validate email addresses before sending to improve deliverability

Overview

The email validation API checks an address for syntax errors, disposable domains, role-based prefixes, free providers, and valid MX records -- all in a single request. Use it to clean signup forms, verify recipient lists, or gate sending to reduce bounces and protect your sender reputation.

API Reference

Validate an Email Address

POST /v1/validate

Requires an API key with the emails:validate scope.

curl -X POST https://api.euromail.dev/v1/validate \
  -H "X-EuroMail-Api-Key: em_live_..." \
  -H "Content-Type: application/json" \
  -d '{"email": "[email protected]"}'

Request:

Field	Required	Description
`email`	Yes	The email address to validate. Accepts bare addresses (`[email protected]`) and display-name format (`"Jane Doe" <[email protected]>`).

Response:

Field	Type	Description
`email`	string	The validated address (echoed back)
`valid`	boolean	Overall validity. `false` if disposable, invalid syntax, or no MX records.
`deliverable`	string	`"yes"`, `"no"`, or `"unknown"`
`is_disposable`	boolean	Whether the domain is a known disposable email provider
`is_role`	boolean	Whether the local part matches a role-based prefix (e.g. `admin@`, `support@`)
`is_free`	boolean	Whether the domain is a known free email provider (e.g. Gmail, Yahoo)
`mx_found`	boolean	Whether MX records were found for the domain
`reason`	string or null	Explanation when validation fails

Validation Checks

Each request runs five checks in sequence:

1. RFC 5322 Syntax

Validates the address against a practical subset of RFC 5322:

Local part (before @): 1-64 characters. Alphanumeric plus . + - _ ! # $ % & ' * / = ? ^ { | } ~. No leading, trailing, or consecutive dots.
Domain part (after @): 1-253 characters. Valid hostname labels separated by dots. Labels are 1-63 characters, alphanumeric plus hyphen, no leading or trailing hyphens. At least one dot required.

2. Disposable Domain Detection

Checks the domain against a list of 1,001 known disposable email providers (mailinator.com, 10minutemail.com, guerrillamail.com, etc.). The list is compiled at build time for fast lookup.

3. Role-Based Address Detection

Checks whether the local part matches one of 43 role-based prefixes:

abuse, admin, administrator, billing, compliance, devnull, dns, ftp, help, hostmaster, info, mailer-daemon, marketing, media, no-reply, noc, noreply, office, operations, postmaster, privacy, registrar, remove, root, sales, security, spam, ssladmin, support, sysadmin, tech, undisclosed-recipients, unsubscribe, usenet, uucp, webmaster, www

Role-based addresses are often shared inboxes and tend to generate more complaints. The is_role flag lets you decide whether to accept them.

4. Free Provider Detection

Checks the domain against 56 known free email providers, including:

Gmail: gmail.com, googlemail.com
Yahoo: yahoo.com and regional variants (yahoo.co.uk, yahoo.co.jp, yahoo.fr, yahoo.de, etc.)
Microsoft: outlook.com, hotmail.com, live.com, msn.com and regional variants
Apple: icloud.com, me.com, mac.com
Privacy-focused: protonmail.com, protonmail.ch, proton.me, pm.me, tutanota.com, tuta.io
European: gmx.com, gmx.de, web.de, t-online.de
Other: aol.com, mail.com, zoho.com, fastmail.com, yandex.com, mail.ru

5. MX Record Lookup

Performs an asynchronous DNS lookup for MX records on the domain. Results are cached for 1 hour (up to 10,000 domains) to avoid redundant lookups. The lookup has a 5-second timeout with 2 retry attempts.

MX found: The domain has at least one MX record and can receive email.
MX not found (definitive): The domain returned NXDOMAIN or no records. This result is cached.
MX lookup failed (transient): A timeout or network error occurred. The result is not cached and deliverable is set to "unknown".

Decision Logic

The checks determine the final valid and deliverable values:

Condition	`valid`	`deliverable`	`reason`
Disposable domain	`false`	`"no"`	"Disposable email domain"
No MX records (definitive)	`false`	`"no"`	"No MX records found for domain"
MX lookup timed out	`true`	`"unknown"`	Error message from DNS resolver
All checks passed	`true`	`"yes"`	`null`

Note that is_role and is_free are informational flags. They do not affect valid or deliverable.

Response Examples

Valid email

{
  "email": "[email protected]",
  "valid": true,
  "deliverable": "yes",
  "is_disposable": false,
  "is_role": false,
  "is_free": true,
  "mx_found": true,
  "reason": null
}

Disposable domain

{
  "email": "[email protected]",
  "valid": false,
  "deliverable": "no",
  "is_disposable": true,
  "is_role": false,
  "is_free": false,
  "mx_found": true,
  "reason": "Disposable email domain"
}

Role-based address

{
  "email": "[email protected]",
  "valid": true,
  "deliverable": "yes",
  "is_disposable": false,
  "is_role": true,
  "is_free": false,
  "mx_found": true,
  "reason": null
}

No MX records

{
  "email": "[email protected]",
  "valid": false,
  "deliverable": "no",
  "is_disposable": false,
  "is_role": false,
  "is_free": false,
  "mx_found": false,
  "reason": "No MX records found for domain"
}

Use Cases

Signup form validation -- Call /v1/validate when a user registers. Reject disposable domains, warn on deliverable: "unknown", and flag role-based addresses for review.

List cleaning -- Before importing a recipient list, validate each address in batch. Remove entries where valid is false to reduce hard bounces.

Pre-send checks -- Validate the to address before calling /v1/emails to avoid wasting quota on undeliverable addresses.