Pragmatic.Email

Email for .NET without a third-party mail library: SMTP with connection pooling, DKIM / S/MIME signing, a middleware pipeline, and first-class testing support.

The Problem

Sending email in .NET usually means pulling in MailKit (200K+ lines, dozens of transitive dependencies) for what should be straightforward, and you still hand-wire the message, with no connection pooling and no pipeline.

// Typical MailKit setup: new TCP connection every time, no pipeline
using var client = new SmtpClient();
await client.ConnectAsync("smtp.hotel.com", 587, SecureSocketOptions.StartTls);
await client.AuthenticateAsync("user", "pass");
await client.SendAsync(message);
await client.DisconnectAsync(true);

The Solution

A small email library (it depends only on Microsoft.Extensions.* abstractions and System.Security.Cryptography.Pkcs) with a fluent message API, pooled SMTP connections, optional DKIM/S-MIME signing, a middleware pipeline and in-memory/file transports for tests. The shipped middleware are DefaultFromMiddleware, DkimMiddleware and SmimeMiddleware; add your own with EmailBuilder.AddMiddleware<T>().

var message = new EmailMessageBuilder()
    .From("booking@hotel.com", "Hotel Booking")
    .To(guest.Email)
    .Subject("Reservation Confirmed")
    .HtmlBody("<h1>Confirmed</h1>...")
    .TextBody("Confirmed ...")
    .Attach("invoice.pdf", pdfBytes, "application/pdf")
    .Build();

EmailResult sent = await emailSender.SendAsync(message);   // IEmailSender

This module sends; it does not write the body. A mail a person reads comes from a .pdxemail template resolved against data (Pragmatic.Email.Templates, Pragmatic.Email.Model and Pragmatic.Documents.Email, all part of Pragmatic.Documents) and its HTML and text go into HtmlBody / TextBody here. See HTML email rendering.

Connections are pooled across sends; configure the transport once in the host. The builder validates addresses as you add them, so a malformed one fails where you wrote it rather than at send time.

Installation

dotnet add package Pragmatic.Email
dotnet add package Pragmatic.Email.Testing   # InMemoryTransport, FileTransport: test projects only

Status

Functional within 1.0.0-alpha: SMTP transport, pooling, DKIM and S/MIME signing, the middleware pipeline, and test support. See the roadmap.

TLS is negotiated with STARTTLS by default and switches to implicit TLS (SMTPS) automatically on port 465; set UseImplicitTls to force either mode. TimeoutSeconds bounds connect, reads and writes.

Known limit: bodies are sent as 8bit; quoted-printable is not implemented.

| Concepts | Message model, transport, pooling, the middleware pipeline | | Getting Started | Send your first email, configure SMTP, test it | | Common Mistakes | The most frequent email pitfalls | | Troubleshooting | Problem/solution guide |

Requirements

• .NET 10.0+

License

Part of the Pragmatic.Design ecosystem. See Licensing. Pragmatic.Email is licensed under the PolyForm Small Business 1.0.0 license (free for small businesses; commercial license above the threshold).