Refactor SMTPSocket and SMTP with a specifically no-auth constructor.

Sources/SwiftSMTP/SMTP.swift

@@ -93,6 +93,39 @@ public struct SMTP {
         self.timeout = timeout
     }
 
+    /// Initializes an `SMTP` instance, specifically for use when communicating with an SMTP
+    /// host which does not perform authentication.
+    ///
+    /// - Parameters:
+    ///     - hostname: Hostname of the SMTP server to connect to, i.e. `smtp.example.com`.
+    ///     - port: Port to connect to the server on. Defaults to `465`.
+    ///     - tlsMode: TLSMode `enum` indicating what form of connection security to use.
+    ///     - tlsConfiguration: `TLSConfiguration` used to connect with TLS. If nil, a configuration with no backing
+    ///       certificates is used. See `TLSConfiguration` for other configuration options.
+    ///     - domainName: Client domain name used when communicating with the server. Defaults to `localhost`.
+    ///     - timeout: How long to try connecting to the server to before returning an error. Defaults to `10` seconds.
+    ///
+    /// - Note:
+    ///     - You may need to enable access for less secure apps for your account on the SMTP server.
+    ///     - Some servers like Gmail support IPv6, and if your network does  not, you will first attempt to connect via
+    ///       IPv6, then timeout, and fall back to IPv4. You can avoid this by disabling IPv6 on your machine.
+    public init(hostname: String,
+                port: Int32 = 587,
+                tlsMode: TLSMode = .requireSTARTTLS,
+                tlsConfiguration: TLSConfiguration? = nil,
+                domainName: String = "localhost",
+                timeout: UInt = 10) {
+        self.hostname = hostname
+        self.email = ""
+        self.password = ""
+        self.port = port
+        self.tlsMode = tlsMode
+        self.tlsConfiguration = tlsConfiguration
+        self.authMethods = [String: AuthMethod]()
+        self.domainName = domainName
+        self.timeout = timeout
+    }
+
     /// Send an email.
     ///
     /// - Parameters:

Sources/SwiftSMTP/SMTPSocket.swift

@@ -31,6 +31,40 @@ struct SMTPSocket {
          domainName: String,
          timeout: UInt) throws {
         socket = try Socket.create()
+        let serverOptions = try setupSocket(hostname: hostname,
+                                            port: port,
+                                            tlsMode: tlsMode,
+                                            tlsConfiguration: tlsConfiguration,
+                                            domainName: domainName,
+                                            timeout: timeout)
+        let authMethod = try getAuthMethod(authMethods: authMethods, serverOptions: serverOptions, hostname: hostname)
+        try login(authMethod: authMethod, email: email, password: password)
+    }
+
+
+    /// Initializer for an SMTPSocket when you want to connect to a server that does not
+    /// require authentication to send messages.
+    init(hostname: String,
+         port: Int32,
+         tlsMode: SMTP.TLSMode,
+         tlsConfiguration: TLSConfiguration?,
+         domainName: String,
+         timeout: UInt) throws {
+        socket = try Socket.create()
+        _ = try setupSocket(hostname: hostname,
+                            port: port,
+                            tlsMode: tlsMode,
+                            tlsConfiguration: tlsConfiguration,
+                            domainName: domainName,
+                            timeout: timeout)
+    }
+
+    private func setupSocket(hostname: String,
+                             port: Int32,
+                             tlsMode: SMTP.TLSMode,
+                             tlsConfiguration: TLSConfiguration?,
+                             domainName: String,
+                             timeout: UInt) throws -> [Response] {
         if tlsMode == .requireTLS {
             if let tlsConfiguration = tlsConfiguration {
                 socket.delegate = try tlsConfiguration.makeSSLService()
@@ -48,10 +82,7 @@ struct SMTPSocket {
                 throw SMTPError.requiredSTARTTLS
             }
         }
-        let authMethod = try getAuthMethod(authMethods: authMethods, serverOptions: serverOptions, hostname: hostname)
-        if authMethod != .none {
-            try login(authMethod: authMethod, email: email, password: password)
-        }
+        return serverOptions
     }
 
     func write(_ text: String) throws {

Tests/SwiftSMTPTests/TestMailSender.swift

@@ -57,6 +57,23 @@ class TestMailSender: XCTestCase {
             x.fulfill()
         }
     }
+
+    func testSendMailNoAuth() throws {
+        let x = expectation(description: #function)
+        defer { waitForExpectations(timeout: testDuration) }
+
+        let mail = Mail(from: from, to: [to], subject: #function, text: text)
+        if let theHost = noAuthHost {
+            let noAuthSMTP = SMTP(hostname: theHost, port: noAuthPort, tlsMode: .ignoreTLS,
+                                  tlsConfiguration: .none)
+            noAuthSMTP.send(mail) { (err) in
+                XCTAssertNil(err, String(describing: err))
+                x.fulfill()
+            }
+        } else {
+            throw XCTSkip("No no-auth SMTP server configured")
+        }
+    }
 
     func testSendMailInArray() {
         let x = expectation(description: #function)

Tests/SwiftSMTPTests/TestSMTPSocket.swift

@@ -36,12 +36,9 @@ class TestSMTPSocket: XCTestCase {
             do {
                 _ = try SMTPSocket(
                     hostname: noAuthHost,
-                    email: email,
-                    password: "don't care",
                     port: noAuthPort,
                     tlsMode: .ignoreTLS,
                     tlsConfiguration: nil,
-                    authMethods: [String: AuthMethod](),
                     domainName: domainName,
                     timeout: timeout
                 )