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

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

fmt.Println("email validation result", ret) /* result is: { "email":"[email protected]", "disposable":false, "reachable":"unknown", "role_account":false, "free":false, "syntax":{ "username":"example", "domain":"exampledomain.org", "valid":true }, "has_mx_records":true, "smtp":null, "gravatar":null } */ }

### Email verification Lookup

Use CheckSMTP to performs an email verification lookup via SMTP.

func main() {

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

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

}

If you want to disable catchAll checking, use the DisableCatchAllCheck() switch (in effect only when SMTP verification is enabled).

> 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

> Note: set FromEmail() and HelloName() before verifying at any volume. The defaults are
> [email protected] and localhost, and example.org is reserved by RFC 2606, so a server
> that validates the sender can reject the whole exchange before it ever considers the
> address you asked about. Rejections of this kind arrive at MAIL FROM and name the sender
> or the connecting host rather than the recipient, for example
> 550 5.7.25 Forward-confirmed reverse DNS failed or
> 550 5.7.1 Service unavailable, Client host [...] blocked using Spamhaus. Use a domain you
> control, with a PTR record for the IP you connect from.

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

The protocol could be socks5, socks4 and socks4a.

func main() {

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

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

}

Two things to know about the proxy:

> A query string in the proxy URI is ignored. golang.org/x/net/proxy reads only the
> scheme, credentials and host, so a ?timeout=5s has no effect. Use ConnectTimeout() and
> OperationTimeout() instead.

> DNS does not go through the proxy. Only the connection to the mail server does, so MX
> lookups still leave from the local machine. To route them through the proxy as well, dial
> your DNS server over TCP through it — SOCKS5 carries TCP, and Go frames DNS over a
> non-packet connection per RFC 7766:
>
>

socksDialer, err := proxy.SOCKS5("tcp", "127.0.0.1:1080", nil, proxy.Direct)

if err != nil {

return err

}

verifier = emailverifier.

NewVerifier().

EnableSMTPCheck().

Proxy("socks5://127.0.0.1:1080").

Resolver(&net.Resolver{

PreferGo: true,

Dial: func(ctx context.Context, network, address string) (net.Conn, error) {

// ignore network, which may be "udp": SOCKS5 CONNECT carries TCP only

return socksDialer.Dial("tcp", "8.8.8.8:53")

},

})

>

By default, the verifier uses net.DefaultResolver (the platform's system-configured DNS resolver) for MX lookups and direct SMTP host lookups. You can override this behaviour by supplying your own *net.Resolver via Resolver(), for example to query a specific DNS server. When a proxy is configured, SMTP hostname resolution follows the proxy path rather than this resolver. MX record lookups always use this resolver, whether or not a proxy is set.go var ( verifier = emailverifier. NewVerifier(). EnableSMTPCheck(). Resolver(&net.Resolver{ PreferGo: true, Dial: func(ctx context.Context, network, address string) (net.Conn, error) { d := net.Dialer{} return d.DialContext(ctx, network, "8.8.8.8:53") }, }) )

func main() {

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

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

}

> Note: PreferGo: true is doing real work here, it is not boilerplate. MX record lookups always
> go through Go's own DNS client, so a custom Dial is honoured for those either way. Resolving
> the mail server's hostname to an IP for the TCP connection is different: without PreferGo that
> step may use the system (cgo) resolver, which ignores Dial entirely and quietly falls back to
> /etc/resolv.conf. Even with it set, /etc/hosts is still consulted before DNS, so a host
> listed there never reaches your resolver.

Misc Validation
To check if an email domain is disposable via IsDisposable

func main() { domain := "domain.org" if verifier.IsDisposable(domain) { fmt.Printf("%s is a disposable domain\n", domain) return } 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

API

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.

Similar Libraries Comparison

| | email-verifier | trumail | check-if-email-exists | freemail | | ----------------------------------- | :----------------------------------------------------------: | :-------------------------------------------: | :---------------------------------------------: | :-----------------------------------------------: | | Features | 〰️ | 〰️ | 〰️ | 〰️ | | Disposable email address validation | ✅ | ✅, but not available in free lib | ✅ | ✅ | | Disposable address autoupdate | ✅ | 🤔 | ❌ | ❌ | | Free email provider check | ✅ | ✅, but not available in free lib | ❌ | ✅ | | Role account validation | ✅ | ❌ | ✅ | ❌ | | Syntax validation | ✅ | ✅ | ✅ | ❌ | | Email reachability | ✅ | ✅ | ✅ | ❌ | | DNS records validation | ✅ | ✅ | ✅ | ❌ | | Email deliverability | ✅ | ✅ | ✅ | ❌ | | Mailbox disabled | ✅ | ✅ | ✅ | ❌ | | Full inbox | ✅ | ✅ | ✅ | ❌ | | Host exists | ✅ | ✅ | ✅ | ❌ | | Catch-all | ✅ | ✅ | ✅ | ❌ | | Gravatar | ✅ | ✅, but not available in free lib | ❌ | ❌ | | Typo check | ✅ | ✅, but not available in free lib | ❌ | ❌ | | Use proxy to connect over SMTP | ✅ | ❌ | ✅ | ❌ | | Honeyport dection | 🔜 | ❌ | ❌ | ❌ | | Bounce email check | 🔜 | ❌ | ❌ | ❌ | | Tech | 〰️ | 〰️ | 〰️ | 〰️ | | Provide API | ✅ | ✅ | ✅ | ❌ | | Free API | ✅ | ❌ | ❌ | ❌ | | Language | Go | Go | Rust | JavaScript | | Active maintain | ✅ | ❌ | ✅ | ✅ | | High Performance | ✅ | ❌ | ✅ | ✅ |

FAQ

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

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

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.

Credits