Fix the broken SMTP sending

examples/main.go

@@ -22,10 +22,9 @@ var DatabaseBackend = smtp.DatabaseBackend{
 
 // AuthenticationBackend is a smtp.AuthenticationBackend implementation that always returns a fixed address for Authenticate.
 var AuthenticationBackend = smtp.AuthenticationBackend{
-	Authenticate: func(initial string, conn *textproto.Conn) (*smtp.Address, error) {
-		return &smtp.Address{
-			Name:    "test",
-			Address: "example.org",
+	Authenticate: func(initial string, conn *textproto.Conn) (smtp.CheckAddress, error) {
+		return func(address *smtp.Address) (bool, error) {
+			return true, nil
 		}, nil
 	},
 }

smtp.go

@@ -58,7 +58,8 @@ type DatabaseBackend struct {
 
 // AuthenticationBackend is a struct that represents an authentication backend
 type AuthenticationBackend struct {
-	Authenticate func(initial string, conn *textproto.Conn) (CheckAddress, error)
+	Authenticate        func(initial string, conn *textproto.Conn) (CheckAddress, error)
+	SupportedMechanisms []string
 }
 
 type CheckAddress func(*Address) (bool, error)
@@ -211,8 +212,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 		return
 	}
 
-	fmt.Println("Connection from", conn.RemoteAddr().String())
-
 	for {
 		line, err := textProto.ReadLine()
 		if err != nil {
@@ -283,6 +282,9 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 				if fr.enforceTLS {
 					capabilities = append(capabilities, "250-REQUIRETLS")
 				}
+				if fr.auth.SupportedMechanisms != nil {
+					capabilities = append(capabilities, "250-AUTH "+strings.Join(fr.auth.SupportedMechanisms, " "))
+				}
 				capabilities = append(capabilities, defaultCapabilities...)
 				state.HELO = true
 				err = speakMultiLine(textProto, capabilities)
@@ -324,7 +326,7 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 			} else {
 				checkAddress, err := fr.auth.Authenticate(strings.TrimPrefix(line, "AUTH "), textProto)
 				if err != nil {
-					_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
+					_ = textProto.PrintfLine(err.Error())
 					_ = conn.Close()
 					return
 				}
@@ -588,7 +590,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 					Host: strings.Split(conn.RemoteAddr().String(), ":")[0],
 				}
 				go sendEmail(SenderArgs{
-					Hostname:   fr.hostname,
 					EnforceTLS: fr.enforceTLS,
 				}, mail, fr.database, queueID)
 
@@ -617,7 +618,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 
 // SenderArgs is a struct that represents the arguments for the Sender
 type SenderArgs struct {
-	Hostname   string
 	EnforceTLS bool
 }
 
@@ -648,7 +648,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 		return errors.New("unexpected greeting - " + line)
 	}
 
-	err = textConn.PrintfLine("EHLO %s", args.Hostname)
+	err = textConn.PrintfLine("EHLO %s", mxHost)
 	if err != nil {
 		return err
 	}
@@ -682,16 +682,11 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 			InsecureSkipVerify: false,
 		})
 
-		err = tlsConn.Handshake()
-		if err != nil {
-			return err
-		}
-
 		textConn = textproto.NewConn(tlsConn)
 
 		// Just use HELO, no point using EHLO when we already have all the capabilities
 		// This also gets us out of using readMultilineCodeResponse
-		err = textConn.PrintfLine("HELO %s", args.Hostname)
+		err = textConn.PrintfLine("HELO %s", mxHost)
 		if err != nil {
 			return err
 		}
@@ -714,10 +709,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		// For some reason the EHLO stuff ends up here
-		fmt.Println("5")
 		return err
 	}
 
@@ -732,9 +724,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 		}
 
 		code, line, err = textConn.ReadCodeLine(0)
-		fmt.Println(code, line, err)
 		if err != nil {
-			fmt.Println("6")
 			return err
 		}
 
@@ -749,9 +739,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("7")
 		return err
 	}
 
@@ -771,9 +759,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("8")
 		return err
 	}
 
@@ -787,9 +773,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("9")
 		return err
 	}