Refactor error handling in message delivery process

The error handling process in sending messages has been refactored for better accuracy and efficiency. Instead of immediately joining errors and returning, they are now collected in a slice and joined in a deferred function to ensure all errors are captured before being returned. Furthermore, the SendError structure has been updated to include a reference to the affected message, providing better context for each error.

client_120.go

@@ -18,25 +18,33 @@ func (c *Client) Send(messages ...*Msg) (returnErr error) {
 		returnErr = &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err)}
 		return
 	}
-	for _, message := range messages {
+
+	var errs []error
+	defer func() {
+		returnErr = errors.Join(errs...)
+	}()
+
+	for msgid, message := range messages {
 		message.sendError = nil
 		if message.encoding == NoEncoding {
 			if ok, _ := c.smtpClient.Extension("8BITMIME"); !ok {
 				message.sendError = &SendError{Reason: ErrNoUnencoded, isTemp: false}
-				returnErr = errors.Join(returnErr, message.sendError)
+				errs = append(errs, message.sendError)
 				continue
 			}
 		}
 		from, err := message.GetSender(false)
 		if err != nil {
-			message.sendError = &SendError{Reason: ErrGetSender, errlist: []error{err}, isTemp: isTempError(err)}
+			message.sendError = &SendError{Reason: ErrGetSender, errlist: []error{err}, isTemp: isTempError(err),
-			returnErr = errors.Join(returnErr, message.sendError)
+				affectedMsg: messages[msgid]}
+			errs = append(errs, message.sendError)
 			continue
 		}
 		rcpts, err := message.GetRecipients()
 		if err != nil {
-			message.sendError = &SendError{Reason: ErrGetRcpts, errlist: []error{err}, isTemp: isTempError(err)}
+			message.sendError = &SendError{Reason: ErrGetRcpts, errlist: []error{err}, isTemp: isTempError(err),
-			returnErr = errors.Join(returnErr, message.sendError)
+				affectedMsg: messages[msgid]}
+			errs = append(errs, message.sendError)
 			continue
 		}
 
@@ -47,9 +55,9 @@ func (c *Client) Send(messages ...*Msg) (returnErr error) {
 		}
 		if err = c.smtpClient.Mail(from); err != nil {
 			message.sendError = &SendError{Reason: ErrSMTPMailFrom, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
-				returnErr = errors.Join(returnErr, resetSendErr)
+				errs = append(errs, resetSendErr)
 			}
 			continue
 		}
@@ -70,40 +78,40 @@ func (c *Client) Send(messages ...*Msg) (returnErr error) {
 		}
 		if failed {
 			if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
-				returnErr = errors.Join(returnErr, resetSendErr)
+				errs = append(errs, resetSendErr)
 			}
 			message.sendError = rcptSendErr
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			continue
 		}
 		writer, err := c.smtpClient.Data()
 		if err != nil {
 			message.sendError = &SendError{Reason: ErrSMTPData, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			continue
 		}
 		_, err = message.WriteTo(writer)
 		if err != nil {
 			message.sendError = &SendError{Reason: ErrWriteContent, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			continue
 		}
 		message.isDelivered = true
 
 		if err = writer.Close(); err != nil {
 			message.sendError = &SendError{Reason: ErrSMTPDataClose, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			continue
 		}
 
 		if err = c.Reset(); err != nil {
 			message.sendError = &SendError{Reason: ErrSMTPReset, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 			continue
 		}
 		if err = c.checkConn(); err != nil {
 			message.sendError = &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err)}
-			returnErr = errors.Join(returnErr, message.sendError)
+			errs = append(errs, message.sendError)
 		}
 	}
 

senderror.go

@@ -56,10 +56,11 @@ const (
 
 // SendError is an error wrapper for delivery errors of the Msg
 type SendError struct {
-	Reason  SendErrReason
+	affectedMsg *Msg
-	isTemp  bool
+	errlist     []error
-	errlist []error
+	isTemp      bool
-	rcpt    []string
+	rcpt        []string
+	Reason      SendErrReason
 }
 
 // SendErrReason represents a comparable reason on why the delivery failed