SwiftNIO SMTP

Lightweight SMTP client built on top of SwiftNIO.

[ ] (https://github.com/BinaryBirds/swift-nio-smtp/releases/tag/1.0.0-beta.1 )

Features

• Async SMTP client build over SwiftNIO
• STARTTLS and SSL support
• AUTH LOGIN
• Raw DATA payload support
• No Foundation framework dependency

Requirements

• Swift 6.1+
• Platforms:
  • macOS 15+
  • iOS 18+
  • tvOS 18+
  • watchOS 11+
  • visionOS 2+

Installation

Use Swift Package Manager; add the dependency to your Package.swift file:

.package(url: "https://github.com/BinaryBirds/swift-nio-smtp", exact: "1.0.0-beta.1"),

Then add NIOSMTP to your target dependencies:

.product(name: "NIOSMTP", package: "swift-nio-smtp"),

Usage

API documentation is available at the following link.

Example

Create an SMTPEnvelope with a raw DATA payload and send it using NIOSMTP.

import NIOSMTP
import NIO
import Logging

let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
let smtp = NIOSMTP(
    eventLoopGroup: eventLoopGroup,
    configuration: .init(
        hostname: "smtp.example.com",
        signInMethod: .credentials(
            username: "user@example.com",
            password: "app-password"
        )
    ),
    logger: .init(label: "nio-smtp")
)

let raw = [
    "From: sender@example.com",
    "To: recipient@example.com",
    "Subject: Hello",
    "Date: Mon, 01 Jan 2024 00:00:00 +0000",
    "Message-ID: <message@example.com>",
    "Content-Type: text/plain; charset=\"UTF-8\"",
    "Mime-Version: 1.0",
    "",
    "Hello from SwiftNIO SMTP.",
    ""
].joined(separator: "\r\n")

let envelope = try SMTPEnvelope(
    from: "sender@example.com",
    recipients: ["recipient@example.com"],
    data: raw
)

try await smtp.send(envelope)
try await eventLoopGroup.shutdownGracefully()

Development

• Build: swift build
• Test:
  • local: make test
  • using Docker: make docker-test
• Format: make format
• Check: make check

Contributing

Pull requests are welcome. Please keep changes focused and include tests for new logic.

Credits

The NIOSMTP library is heavily inspired by Mikroservices/Smtp.