SMTPKitten

Create

let mail = Mail(
    from: MailUser(name: "My Mailer", email: "[email protected]"),
    to: [MailUser(name: "John Doe", email: "[email protected]")],
    subject: "Welcome to our app!",
    contentType: .plain,
    text: "Welcome to our app, you're all set up & stuff."
)

SMTPClient.connect(
    hostname: "smtp.example.com",
    ssl: .startTLS(configuration: .default)
).flatMap { client in
    client.login(
        user: "[email protected]",
        password: "pas$w0rd"
    ).flatMap {
        client.sendMail(mail)
    }
}

Multi-part Support

let body = MultiPartBody(withParts: [
    MultiPartTextPart(text: "Hello from there!"),
    MultiPartAlternativePart(plainText: "Just a plain text", htmlText: "<h2>Just a HTML</h2>"),
    MultiPartFilePart(mime: "image/jpg",
                      fileName: "Star.jpg",
                      fileBody: "IDEwNiAwIFIKPj4Kc3RhcnR4cmVmCjgwNDkzCiUlRU9GCg=="),    // Base64-encoded file
    MultiPartFilePart(mime: "application/pdf",
                      fileName: "Guide.pdf",
                      fileBody: "IDEwNiAwIFIKPj4Kc3RhcnR4cmVmCjgwNDkzCiUlRU9GCg=="),    // Base64-encoded file
])

let mail = Mail(
    from: MailUser(name: "My Mailer", email: "[email protected]"),
    to: [MailUser(name: "John Doe", email: "[email protected]")],
    subject: "Some files attached",
    contentType: .init(rawValue: body.contentTypeHeader),
    text: body.string
)

SMTPClient.connect(...)

Note you should set the "global" Content-Type header and the mail message body to the values provided by MultiPartBody.