You can use CSharp's built in SMTP client package `System.Net.Mail`. Let us use XUnit and the [MailSlurp](/api/) client to create an email address and send emails to it.

## How does it work?

First add the package to your [CSharp project](/docs/csharp/)

```
dotnet add package mailslurp
dotnet restore
```

Configure your MailSlurp API Key with the email client:

```csharp
using mailslurp.Api;
using mailslurp.Client;
using mailslurp.Model;

var config = new Configuration();
config.ApiKey.Add("x-api-key", "your_api_key_here");
```

Then you can create inboxes during tests or in your application to [connect to SMTP](/guides/smtp/csharp-send-email-smtp/):

```csharp
var apiInstance = new InboxControllerApi(config);
var inbox = apiInstance.CreateInbox();

Assert.NotNull(inbox);
Assert.Contains("@mailslurp.com", inbox.EmailAddress);
```

## Example XUnit tests

Using XUnit you can connect to SMTP mailboxes during tests and send and receive emails.

```csharp
using System;
using System.Net;
using System.Net.Mail;
using mailslurp.Api;
using mailslurp.Client;
using mailslurp.Model;
using Xunit;

namespace SmtpService.Tests
{
    public class UnitTest1
    {
        [Fact]
        public void CanSendEmailWithMailSlurpSmtp()
        {
            var apiKey = Environment.GetEnvironmentVariable("API_KEY")
                         ?? throw new ArgumentNullException("Missing API_KEY environment variable containing MailSlurp key");

            // configure client
            var config = new Configuration();
            config.ApiKey.Add("x-api-key", apiKey);
            var inboxController = new InboxControllerApi(config);

            // create an smtp inbox
            var inbox = inboxController.CreateInboxWithOptions(new CreateInboxDto(
                inboxType: CreateInboxDto.InboxTypeEnum.SMTPINBOX
            ));
            Assert.Contains("@mailslurp.mx", inbox.EmailAddress);

            // get smtp host, port, password, username etc
            var imapSmtpAccessDetails = inboxController.GetImapSmtpAccess();
            var smtpClient = new SmtpClient(imapSmtpAccessDetails.SmtpServerHost)
            {
                Port = imapSmtpAccessDetails.SmtpServerPort,
                Credentials = new NetworkCredential(userName: imapSmtpAccessDetails.SmtpUsername, password: imapSmtpAccessDetails.SmtpPassword),
                // disable ssl recommended
                EnableSsl = false
            };
            Assert

            // send email to inbox
            smtpClient.Send(from: "test@external.com", recipients: inbox.EmailAddress, subject: "This inbound", body: "Hello");

            // wait for email to arrive
            var waitController = new WaitForControllerApi(config);
            waitController.WaitForLatestEmail(inboxId: inbox.Id, timeout: 30_000);
        }
    }
}
```

## Other use cases

You can use `System.Net.Mail` to send emails in DotNET but what if you want to receive emails instead? Use MailSlurps [email webhooks](/guides/email-webhooks/) to have emails sent directly to your server.

![webhooks](/assets/email-webhooks.svg)

### Receive emails by polling

You can use the waitFor methods with the [MailSlurp SDK client](/docs/csharp/). You can receive emails using waitFor methods on the WaitForControllerApi class.

```csharp
var Timeout = 30000L; // max milliseconds to wait
var UnreadOnly = true; // only count unread emails

var waitForInstance = new WaitForControllerApi(config);
var email = waitForInstance.WaitForLatestEmail(inbox.Id, Timeout, UnreadOnly);

Assert.NotNull(email);
Assert.Equal("Hello", email.Subject);
Assert.Contains("Your code is: ", email.Body);
You can extract content from email bodies using RegExps:


// imagine that email body is `Your code is: 123` and you want to get the number
var rx = new Regex(@"Your code is: ([0-9]{3})", RegexOptions.Compiled);
var match = rx.Match(email.Body);
var code = match.Groups[1].Value;

Assert.Equal("123", code);
```

### Testing OTP email links

A common use case for temporary SMTP mailboxes in Csharp is verifying OTP 2FA login during [integration testing](/guides/email-testing/). OTP one-time passwords are ephemeral codes that can be sent to a user's email address when they want to access a web application or mobile app.

See the [OTP testing guide](/guides/otp-one-time-password-email-test/) for more information.

![cypress js](/assets/read-email-cypress-js.jpg)