Update error handling to include error code and status

Previously, only the isTemp flag was considered when aggregating errors. Now, the error code and enhanced status code from the last error are also included. This ensures more comprehensive error reporting and handling.

client.go

@@ -1190,6 +1190,7 @@ func (c *Client) auth() error {
 func (c *Client) sendSingleMsg(message *Msg) error {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+	escSupport, _ := c.smtpClient.Extension("ENHANCEDSTATUSCODES")
 
 	if message.encoding == NoEncoding {
 		if ok, _ := c.smtpClient.Extension("8BITMIME"); !ok {
@@ -1200,14 +1201,16 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 	if err != nil {
 		return &SendError{
 			Reason: ErrGetSender, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 	rcpts, err := message.GetRecipients()
 	if err != nil {
 		return &SendError{
 			Reason: ErrGetRcpts, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 
@@ -1219,7 +1222,8 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 	if err = c.smtpClient.Mail(from); err != nil {
 		retError := &SendError{
 			Reason: ErrSMTPMailFrom, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 		if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
 			retError.errlist = append(retError.errlist, resetSendErr)
@@ -1238,6 +1242,8 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 			rcptSendErr.errlist = append(rcptSendErr.errlist, err)
 			rcptSendErr.rcpt = append(rcptSendErr.rcpt, rcpt)
 			rcptSendErr.isTemp = isTempError(err)
+			rcptSendErr.errcode = errorCode(err)
+			rcptSendErr.enhancedStatusCode = enhancedStatusCode(err, escSupport)
 			hasError = true
 		}
 	}
@@ -1251,20 +1257,23 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 	if err != nil {
 		return &SendError{
 			Reason: ErrSMTPData, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 	_, err = message.WriteTo(writer)
 	if err != nil {
 		return &SendError{
 			Reason: ErrWriteContent, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 	if err = writer.Close(); err != nil {
 		return &SendError{
 			Reason: ErrSMTPDataClose, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 	message.isDelivered = true
@@ -1272,7 +1281,8 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 	if err = c.Reset(); err != nil {
 		return &SendError{
 			Reason: ErrSMTPReset, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
+			affectedMsg: message, errcode: errorCode(err),
+			enhancedStatusCode: enhancedStatusCode(err, escSupport),
 		}
 	}
 	return nil

client_119.go

@@ -27,8 +27,13 @@ import "errors"
 //   - An error that represents the sending result, which may include multiple SendErrors if
 //     any occurred; otherwise, returns nil.
 func (c *Client) Send(messages ...*Msg) error {
+	escSupport := false
+	if c.smtpClient != nil {
+		escSupport, _ = c.smtpClient.Extension("ENHANCEDSTATUSCODES")
+	}
 	if err := c.checkConn(); err != nil {
-		return &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err)}
+		return &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err),
+			errcode: errorCode(err), enhancedStatusCode: enhancedStatusCode(err, escSupport)}
 	}
 	var errs []*SendError
 	for id, message := range messages {
@@ -50,9 +55,11 @@ func (c *Client) Send(messages ...*Msg) error {
 				returnErr.rcpt = append(returnErr.rcpt, errs[i].rcpt...)
 			}
 
-			// We assume that the isTemp flag from the last error we received should be the
+			// We assume that the error codes and flags from the last error we received should be the
 			// indicator for the returned isTemp flag as well
 			returnErr.isTemp = errs[len(errs)-1].isTemp
+			returnErr.errcode = errs[len(errs)-1].errcode
+			returnErr.enhancedStatusCode = errs[len(errs)-1].enhancedStatusCode
 
 			return returnErr
 		}

client_test.go

@@ -35,7 +35,7 @@ const (
 	// TestServerAddr is the address the simple SMTP test server listens on
 	TestServerAddr = "127.0.0.1"
 	// TestServerPortBase is the base port for the simple SMTP test server
-	TestServerPortBase = 12025
+	TestServerPortBase = 30025
 	// TestSenderValid is a test sender email address considered valid for sending test emails.
 	TestSenderValid = "valid-from@domain.tld"
 	// TestRcptValid is a test recipient email address considered valid for sending test emails.
@@ -3148,6 +3148,59 @@ func TestClient_sendSingleMsg(t *testing.T) {
 			t.Errorf("expected ErrSMTPDataClose, got %s", sendErr.Reason)
 		}
 	})
+	t.Run("error code and enhanced status code support", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-ENHANCEDSTATUSCODES\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailOnMailFrom: true,
+				FeatureSet:     featureSet,
+				ListenPort:     serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		message := testMessage(t)
+
+		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+		t.Cleanup(cancelDial)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		if err = client.DialWithContext(ctxDial); err != nil {
+			var netErr net.Error
+			if errors.As(err, &netErr) && netErr.Timeout() {
+				t.Skip("failed to connect to the test server due to timeout")
+			}
+			t.Fatalf("failed to connect to test server: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := client.Close(); err != nil {
+				t.Errorf("failed to close client: %s", err)
+			}
+		})
+		if err = client.sendSingleMsg(message); err == nil {
+			t.Error("expected mail delivery to fail")
+		}
+		var sendErr *SendError
+		if !errors.As(err, &sendErr) {
+			t.Fatalf("expected SendError, got %s", err)
+		}
+		if sendErr.errcode != 500 {
+			t.Errorf("expected error code 500, got %d", sendErr.errcode)
+		}
+		if !strings.EqualFold(sendErr.enhancedStatusCode, "5.5.2") {
+			t.Errorf("expected enhanced status code 5.5.2, got %s", sendErr.enhancedStatusCode)
+		}
+	})
 }
 
 func TestClient_checkConn(t *testing.T) {

senderror.go

@@ -6,6 +6,8 @@ package mail
 
 import (
 	"errors"
+	"regexp"
+	"strconv"
 	"strings"
 )
 
@@ -60,11 +62,13 @@ const (
 // details about the affected message, a list of errors, the recipient list, and whether
 // the error is temporary or permanent. It also includes a reason code for the error.
 type SendError struct {
-	affectedMsg *Msg
-	errlist     []error
-	isTemp      bool
-	rcpt        []string
-	Reason      SendErrReason
+	affectedMsg        *Msg
+	errcode            int
+	enhancedStatusCode string
+	errlist            []error
+	isTemp             bool
+	rcpt               []string
+	Reason             SendErrReason
 }
 
 // SendErrReason represents a comparable reason on why the delivery failed
@@ -175,6 +179,42 @@ func (e *SendError) Msg() *Msg {
 	return e.affectedMsg
 }
 
+// EnhancedStatusCode returns the enhanced status code of the server response if the
+// server supports it, as described in RFC 2034.
+//
+// This function retrieves the enhanced status code of an error returned by the server. This
+// requires that the receiving server supports this SMTP extension as described in RFC 2034.
+// Since this is the SendError interface, we only collect status codes for error responses,
+// meaning 4xx or 5xx. If the server does not support the ENHANCEDSTATUSCODES extension or
+// the error did not include an enhanced status code, it will return an empty string.
+//
+// Returns:
+//   - The enhanced status code as returned by the server, or an empty string is not supported.
+//
+// References:
+//   - https://datatracker.ietf.org/doc/html/rfc2034
+func (e *SendError) EnhancedStatusCode() string {
+	if e == nil {
+		return ""
+	}
+	return e.enhancedStatusCode
+}
+
+// ErrorCode returns the error code of the server response.
+//
+// This function retrieves the error code the error returned by the server. The error code will
+// start with 5 on permanent errors and with 4 on a temporary error. If the error is not returned
+// by the server, but is generated by go-mail, the code will be 0.
+//
+// Returns:
+//   - The error code as returned by the server, or 0 if not a server error.
+func (e *SendError) ErrorCode() int {
+	if e == nil {
+		return 0
+	}
+	return e.errcode
+}
+
 // String satisfies the fmt.Stringer interface for the SendErrReason type.
 //
 // This function converts the SendErrReason into a human-readable string representation based
@@ -224,3 +264,39 @@ func (r SendErrReason) String() string {
 func isTempError(err error) bool {
 	return err.Error()[0] == '4'
 }
+
+func errorCode(err error) int {
+	rootErr := errors.Unwrap(err)
+	if rootErr != nil {
+		err = rootErr
+	}
+	firstrune := err.Error()[0]
+	if firstrune < 52 || firstrune > 53 {
+		return 0
+	}
+	code := err.Error()[0:3]
+	errcode, cerr := strconv.Atoi(code)
+	if cerr != nil {
+		return 0
+	}
+	return errcode
+}
+
+func enhancedStatusCode(err error, supported bool) string {
+	if err == nil || !supported {
+		return ""
+	}
+	rootErr := errors.Unwrap(err)
+	if rootErr != nil {
+		err = rootErr
+	}
+	firstrune := err.Error()[0]
+	if firstrune != 50 && firstrune != 52 && firstrune != 53 {
+		return ""
+	}
+	re, rerr := regexp.Compile(`\b([245])\.\d{1,3}\.\d{1,3}\b`)
+	if rerr != nil {
+		return ""
+	}
+	return re.FindString(err.Error())
+}

senderror_test.go

@@ -6,6 +6,7 @@ package mail
 
 import (
 	"errors"
+	"fmt"
 	"strings"
 	"testing"
 )
@@ -218,6 +219,150 @@ func TestSendError_Msg(t *testing.T) {
 	})
 }
 
+func TestSendError_EnhancedStatusCode(t *testing.T) {
+	t.Run("SendError with no enhanced status code", func(t *testing.T) {
+		err := &SendError{
+			errlist: []error{ErrNoRcptAddresses},
+			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
+			Reason:  ErrAmbiguous,
+		}
+		if err.EnhancedStatusCode() != "" {
+			t.Errorf("expected empty enhanced status code, got: %s", err.EnhancedStatusCode())
+		}
+	})
+	t.Run("SendError with enhanced status code", func(t *testing.T) {
+		err := &SendError{
+			errlist:            []error{ErrNoRcptAddresses},
+			rcpt:               []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
+			Reason:             ErrAmbiguous,
+			enhancedStatusCode: "5.7.1",
+		}
+		if err.EnhancedStatusCode() != "5.7.1" {
+			t.Errorf("expected enhanced status code: %s, got: %s", "5.7.1", err.EnhancedStatusCode())
+		}
+	})
+	t.Run("enhanced status code on nil error should return empty string", func(t *testing.T) {
+		var err *SendError
+		if err.EnhancedStatusCode() != "" {
+			t.Error("expected empty enhanced status code on nil-senderror")
+		}
+	})
+}
+
+func TestSendError_ErrorCode(t *testing.T) {
+	t.Run("ErrorCode with a go-mail error should return 0", func(t *testing.T) {
+		err := &SendError{
+			errlist: []error{ErrNoRcptAddresses},
+			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
+			Reason:  ErrAmbiguous,
+			errcode: errorCode(ErrNoRcptAddresses),
+		}
+		if err.ErrorCode() != 0 {
+			t.Errorf("expected error code: %d, got: %d", 0, err.ErrorCode())
+		}
+	})
+	t.Run("SendError with permanent error", func(t *testing.T) {
+		err := &SendError{
+			errlist: []error{ErrNoRcptAddresses},
+			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
+			Reason:  ErrAmbiguous,
+			errcode: errorCode(errors.New("535 5.7.8 Error: authentication failed")),
+		}
+		if err.ErrorCode() != 535 {
+			t.Errorf("expected error code: %d, got: %d", 535, err.ErrorCode())
+		}
+	})
+	t.Run("SendError with temporary error", func(t *testing.T) {
+		err := &SendError{
+			errlist: []error{ErrNoRcptAddresses},
+			rcpt:    []string{"<toni.tester@domain.tld>", "<tina.tester@domain.tld>"},
+			Reason:  ErrAmbiguous,
+			errcode: errorCode(errors.New("441 4.1.0 Server currently unavailable")),
+		}
+		if err.ErrorCode() != 441 {
+			t.Errorf("expected error code: %d, got: %d", 441, err.ErrorCode())
+		}
+	})
+	t.Run("error code on nil error should return 0", func(t *testing.T) {
+		var err *SendError
+		if err.ErrorCode() != 0 {
+			t.Error("expected 0 error code on nil-senderror")
+		}
+	})
+}
+
+func TestSendError_errorCode(t *testing.T) {
+	t.Run("errorCode with a go-mail error should return 0", func(t *testing.T) {
+		code := errorCode(ErrNoRcptAddresses)
+		if code != 0 {
+			t.Errorf("expected error code: %d, got: %d", 0, code)
+		}
+	})
+	t.Run("errorCode with permanent error", func(t *testing.T) {
+		code := errorCode(errors.New("535 5.7.8 Error: authentication failed"))
+		if code != 535 {
+			t.Errorf("expected error code: %d, got: %d", 535, code)
+		}
+	})
+	t.Run("errorCode with temporary error", func(t *testing.T) {
+		code := errorCode(errors.New("443 4.1.0 Server currently unavailable"))
+		if code != 443 {
+			t.Errorf("expected error code: %d, got: %d", 443, code)
+		}
+	})
+	t.Run("errorCode with wrapper error", func(t *testing.T) {
+		code := errorCode(fmt.Errorf("an error occured: %w", errors.New("443 4.1.0 Server currently unavailable")))
+		if code != 443 {
+			t.Errorf("expected error code: %d, got: %d", 443, code)
+		}
+	})
+	t.Run("errorCode with non-4xx and non-5xx error", func(t *testing.T) {
+		code := errorCode(errors.New("220 2.1.0 This is not an error"))
+		if code != 0 {
+			t.Errorf("expected error code: %d, got: %d", 0, code)
+		}
+	})
+	t.Run("errorCode with non 3-digit code", func(t *testing.T) {
+		code := errorCode(errors.New("4xx 4.1.0 The status code is invalid"))
+		if code != 0 {
+			t.Errorf("expected error code: %d, got: %d", 0, code)
+		}
+	})
+}
+
+func TestSendError_enhancedStatusCode(t *testing.T) {
+	t.Run("enhancedStatusCode with nil error should return empty string", func(t *testing.T) {
+		code := enhancedStatusCode(nil, true)
+		if code != "" {
+			t.Errorf("expected empty enhanced status code, got: %s", code)
+		}
+	})
+	t.Run("enhancedStatusCode with error but no support should return empty string", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("553 5.5.3 something went wrong"), false)
+		if code != "" {
+			t.Errorf("expected empty enhanced status code, got: %s", code)
+		}
+	})
+	t.Run("enhancedStatusCode with error and support", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("553 5.5.3 something went wrong"), true)
+		if code != "5.5.3" {
+			t.Errorf("expected enhanced status code: %s, got: %s", "5.5.3", code)
+		}
+	})
+	t.Run("enhancedStatusCode with wrapped error and support", func(t *testing.T) {
+		code := enhancedStatusCode(fmt.Errorf("this error is wrapped: %w", errors.New("553 5.5.3 something went wrong")), true)
+		if code != "5.5.3" {
+			t.Errorf("expected enhanced status code: %s, got: %s", "5.5.3", code)
+		}
+	})
+	t.Run("enhancedStatusCode with 3xx error", func(t *testing.T) {
+		code := enhancedStatusCode(errors.New("300 3.0.0 i don't know what i'm doing"), true)
+		if code != "" {
+			t.Errorf("expected enhanced status code to be empty, got: %s", code)
+		}
+	})
+}
+
 // returnSendError is a helper method to retunr a SendError with a specific reason
 func returnSendError(r SendErrReason, t bool) error {
 	message := NewMsg()