Send with .NET

The usend .NET SDK uses only System.Net.Http and System.Text.Json. You need a verified domain and an API key. It targets .NET 8 or newer.

#1. Install

dotnet add package Usend

#2. Send an email

using Usend;

using var usend = new UsendClient(Environment.GetEnvironmentVariable("USEND_API_KEY"));

try
{
    var sent = await usend.Emails.SendAsync(new
    {
        from = "Acme <[email protected]>",
        to = new[] { "[email protected]" },
        subject = "Hello from usend",
        html = "<p>It works!</p>",
    });
    Console.WriteLine($"queued: {sent.GetProperty("id").GetString()}");
}
catch (UsendException e)
{
    Console.Error.WriteLine($"failed {e.StatusCode} {e.ErrorName}: {e.Message}");
}

Responses are JsonElements. In ASP.NET Core, register one UsendClient as a singleton (or pass your IHttpClientFactory client through UsendClientOptions.HttpClient). Pass an idempotency key to make retries safe: SendAsync(email, UsendClient.NewIdempotencyKey()).

#Verify a webhook

var evt = Webhook.Verify(rawBody, headers, Environment.GetEnvironmentVariable("USEND_WEBHOOK_SECRET")!);

#Plain HTTP and SMTP

You can skip the SDK: POST https://api.usend.et/emails with Authorization: Bearer <key> works from HttpClient.

System.Net.Mail.SmtpClient is obsolete for new code; use MailKit against smtp.usend.et port 587 (STARTTLS) or 465 with username usend and your API key (usend.GetSmtpConfig() returns these settings). See Send with SMTP.