jstedfast/mailkit

★ 6,780C#Audience · developerComplexity · 2/5Setup · easy

Mindmap

mindmap
  root((MailKit))
    Protocols
      SMTP send mail
      IMAP read mail
      POP3 download mail
    Auth methods
      Username password
      OAuth2 tokens
      Proxy routing
    Features
      Async operations
      Cancellation support
      Encryption S/MIME PGP
    Platforms
      Windows
      macOS
      Linux

mindmap root((MailKit)) Protocols SMTP send mail IMAP read mail POP3 download mail Auth methods Username password OAuth2 tokens Proxy routing Features Async operations Cancellation support Encryption S/MIME PGP Platforms Windows macOS Linux

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Things people build with this

USE CASE 1

Build an app that sends automated emails via SMTP with OAuth2 authentication for Gmail or Outlook.

USE CASE 2

Create a background service that monitors an IMAP mailbox and processes incoming messages without blocking the main thread.

USE CASE 3

Add email attachment handling with S/MIME or PGP encryption to a web application.

USE CASE 4

Sync emails from a POP3 server in a desktop client using cancellable async calls.

Tech stack

C#.NETMimeKitNuGetOAuth2S/MIMEPGP

Getting it running

Difficulty · easy Time to first run · 5min

License terms are not described in the explanation.

In plain English

MailKit is a C# library for .NET that gives applications the ability to send and receive email. It handles three standard email protocols: SMTP for sending mail, IMAP for reading and managing mail on a server, and POP3 for downloading mail from a server. The library runs on Windows, macOS, and Linux, and is built on top of a companion library called MimeKit, which handles the structure of email messages, including attachments, HTML bodies, plain text parts, digital signatures, and encryption via S/MIME and PGP. The library covers a wide range of authentication methods, so it works with mail servers that require anything from simple username and password login to OAuth2 tokens used by Gmail, Outlook, and other modern providers. Connections can also be routed through HTTP or SOCKS proxies for environments where direct server access is not possible. For developers, every operation can be cancelled mid-flight, and each action has both a regular version and an asynchronous version that does not block the calling thread while waiting for the mail server to respond. This makes it suitable for desktop apps, web backends, and background services. The IMAP client supports a large number of server extensions, which means it can take advantage of features like server-side sorting, folder sharing, push notifications for new mail, and efficient incremental sync on servers that offer them. The SMTP and POP3 clients similarly handle connection encryption, extension negotiation, and multiple authentication schemes automatically. MailKit is available as a NuGet package and can be added to a project in a single step. Lighter-weight editions of both MailKit and MimeKit are also published for projects that do not need the full feature set.

Copy-paste prompts

Prompt 1

Using MailKit in C#, write async code to connect to Gmail via IMAP with an OAuth2 token, list all unread messages in the inbox, and mark them as read.

Prompt 2

Show me how to use MailKit to send an HTML email with a PDF attachment via SMTP, routing the connection through a SOCKS5 proxy.

Prompt 3

Using MailKit's IMAP client, write a method that enables push notifications for new mail and processes each arriving message asynchronously.

Prompt 4

Write a C# service using MailKit that incrementally syncs an IMAP mailbox, downloading only messages newer than the last sync checkpoint.

Prompt 5

How do I use MimeKit and MailKit together to send a digitally signed S/MIME email from a .NET application?

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