Programming language: Go
License: MIT License
Tags: Email    
Latest version: v1.3.0

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โœ‰๏ธ A Go library for email verification without sending any emails.

Build Status Godoc Coverage Status Go Report Card license


  • Email Address Validation: validates if a string contains a valid email.
  • Email Verification Lookup via SMTP: performs an email verification on the passed email
  • MX Validation: checks the DNS MX records for the given domain name
  • Misc Validation: including Free email provider check, Role account validation, Disposable emails address (DEA) validation
  • Email Reachability: checks how confident in sending an email to the address


Use go get to install this package.

```shell script go get -u github.com/AfterShip/email-verifier

## Usage

### Basic usage

Use `Verify` method to verify an email address with different dimensions

package main

import (

    emailverifier "github.com/AfterShip/email-verifier"

var (
    verifier = emailverifier.NewVerifier()

func main() {
    email := "[email protected]"

    ret, err := verifier.Verify(email)
    if err != nil {
        fmt.Println("verify email address failed, error is: ", err)
    if !ret.Syntax.Valid {
        fmt.Println("email address syntax is invalid")

    fmt.Println("email validation result", ret)
        result is:
            "email":"[email protected]",

Email verification Lookup

Use CheckSMTP to performs an email verification lookup via SMTP.

var (
    verifier = emailverifier.

func main() {

    domain := "domain.org"
    username := "username"
    ret, err := verifier.CheckSMTP(domain, username)
    if err != nil {
        fmt.Println("check smtp failed: ", err)

    fmt.Println("smtp validation result: ", ret)


Note: because most of the ISPs block outgoing SMTP requests through port 25 to prevent email spamming, the module will not perform SMTP checking by default. You can initialize the verifier with EnableSMTPCheck() to enable such capability if port 25 is usable, or use a socks proxy to connect over SMTP

Use a SOCKS5 proxy to verify email

Support setting a SOCKS5 proxy to verify the email, proxyURI should be in the format: socks5://user:[email protected]:1080?timeout=5s

The protocol could be socks5, socks4 and socks4a.

var (
    verifier = emailverifier.
        Proxy("socks5://user:[email protected]:1080?timeout=5s")

func main() {

    domain := "domain.org"
    username := "username"
    ret, err := verifier.CheckSMTP(domain, username)
    if err != nil {
        fmt.Println("check smtp failed: ", err)

    fmt.Println("smtp validation result: ", ret)


Misc Validation

To check if an email domain is disposable via IsDisposable

var (
    verifier = emailverifier.

func main() {
    domain := "domain.org"
    if verifier.IsDisposable(domain) {
        fmt.Printf("%s is a disposable domain\n", domain)
    fmt.Printf("%s is not a disposable domain\n", domain)

Note: It is possible to automatically update the disposable domains daily by initializing verifier with EnableAutoUpdateDisposable()

Suggestions for domain typo

Will check for typos in an email domain in addition to evaluating its validity. If we detect a possible typo, you will find a non-empty "suggestion" field in the validation result containing what we believe to be the correct domain. Also, you can use the SuggestDomain() method alone to check the domain for possible misspellings

func main() {
    domain := "gmai.com"
    suggestion := verifier.SuggestDomain(domain) 
    // suggestion should be `gmail.com`
    if suggestion != "" {
        fmt.Printf("domain %s is misspelled, right domain is %s. \n", domain, suggestion)
    fmt.Printf("domain %s has no possible misspellings. \n", domain)

Note: When using the Verify() method, domain typo checking is not enabled by default, you can enable it in a verifier with EnableDomainSuggest()

For more detailed documentation, please check on godoc.org ๐Ÿ‘‰ email-verifier


We provide a simple self-hosted API server script for reference.

The API interface is very simple. All you need to do is to send a GET request with the following URL.

The email parameter would be the target email you want to verify.


Similar Libraries Comparison

email-verifier trumail check-if-email-exists freemail
Features ใ€ฐ๏ธ ใ€ฐ๏ธ ใ€ฐ๏ธ ใ€ฐ๏ธ
Disposable email address validation โœ… โœ…, but not available in free lib โœ… โœ…
Disposable address autoupdate โœ… ๐Ÿค” โŒ โŒ
Free email provider check โœ… โœ…, but not available in free lib โŒ โœ…
Role account validation โœ… โŒ โœ… โŒ
Syntax validation โœ… โœ… โœ… โŒ
Email reachability โœ… โœ… โœ… โŒ
DNS records validation โœ… โœ… โœ… โŒ
Email deliverability โœ… โœ… โœ… โŒ
Mailbox disabled โœ… โœ… โœ… โŒ
Full inbox โœ… โœ… โœ… โŒ
Host exists โœ… โœ… โœ… โŒ
Catch-all โœ… โœ… โœ… โŒ
Gravatar โœ… โœ…, but not available in free lib โŒ โŒ
Typo check โœ… โœ…, but not available in free lib โŒ โŒ
Use proxy to connect over SMTP โœ… โŒ โœ… โŒ
Honeyport dection ๐Ÿ”œ โŒ โŒ โŒ
Bounce email check ๐Ÿ”œ โŒ โŒ โŒ
Tech ใ€ฐ๏ธ ใ€ฐ๏ธ ใ€ฐ๏ธ ใ€ฐ๏ธ
Provide API โœ… โœ… โœ… โŒ
Free API โœ… โŒ โŒ โŒ
Language Go Go Rust JavaScript
Active maintain โœ… โŒ โœ… โœ…
High Performance โœ… โŒ โœ… โœ…


The library hangs/takes a long time after 30 seconds when performing email verification lookup via SMTP

Most ISPs block outgoing SMTP requests through port 25 to prevent email spamming. email-verifier needs to have this port open to make a connection to the email's SMTP server. With the port being blocked, it is not possible to perform such checking, and it will instead hang until timeout error. Unfortunately, there is no easy workaround for this issue.

For more information, you may also visit this StackOverflow thread.

The output shows "connection refused" in the smtp.error field.

This error can also be due to SMTP ports being blocked by the ISP, see the above answer.

What does reachable: "unknown" means

This means that the server does not allow real-time verification of an email right now, or the email provider is a catch-all email server.



For details on contributing to this repository, see the contributing guide.


This package is licensed under MIT license. See LICENSE for details.

*Note that all licence references and agreements mentioned in the email-verifier README section above are relevant to that project's source code only.