Refactor error handling in message sending loop

Changed from range over messages to range with index to correctly update sendError field in the original messages slice. This prevents shadowing issues and ensures proper error logging for each message.

.github/workflows/codecov.yml

@@ -39,7 +39,7 @@ jobs:
         go: ['1.20', '1.21', '1.22', '1.23']
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
       with:
         egress-policy: audit
 

.github/workflows/codeql-analysis.yml

@@ -45,7 +45,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
       with:
         egress-policy: audit
 
@@ -54,7 +54,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@4dd16135b69a43b6c8efb853346f8437d92d3c93 # v3.26.6
+      uses: github/codeql-action/init@8214744c546c1e5c8f03dde8fab3a7353211988d # v3.26.7
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -65,7 +65,7 @@ jobs:
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@4dd16135b69a43b6c8efb853346f8437d92d3c93 # v3.26.6
+      uses: github/codeql-action/autobuild@8214744c546c1e5c8f03dde8fab3a7353211988d # v3.26.7
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -79,4 +79,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@4dd16135b69a43b6c8efb853346f8437d92d3c93 # v3.26.6
+      uses: github/codeql-action/analyze@8214744c546c1e5c8f03dde8fab3a7353211988d # v3.26.7

.github/workflows/dependency-review.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
         with:
           egress-policy: audit
 

.github/workflows/golangci-lint.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
         with:
           egress-policy: audit
 

.github/workflows/govulncheck.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps: 
     - name: Harden Runner
-      uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
       with:
         egress-policy: audit
     - name: Run govulncheck

.github/workflows/reuse.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps: 
     - name: Harden Runner
-      uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
       with:
         egress-policy: audit
 

.github/workflows/scorecards.yml

@@ -35,7 +35,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
         with:
           egress-policy: audit
 
@@ -75,6 +75,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@4dd16135b69a43b6c8efb853346f8437d92d3c93 # v3.26.6
+        uses: github/codeql-action/upload-sarif@8214744c546c1e5c8f03dde8fab3a7353211988d # v3.26.7
         with:
           sarif_file: results.sarif

.github/workflows/sonarqube.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
+        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
         with:
           egress-policy: audit
 

client_120.go

@@ -24,96 +24,87 @@ func (c *Client) Send(messages ...*Msg) (returnErr error) {
 		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}
-				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),
-				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),
-				affectedMsg: messages[msgid]}
-			errs = append(errs, message.sendError)
-			continue
-		}
-
-		if c.dsn {
-			if c.dsnmrtype != "" {
-				c.smtpClient.SetDSNMailReturnOption(string(c.dsnmrtype))
-			}
-		}
-		if err = c.smtpClient.Mail(from); err != nil {
-			message.sendError = &SendError{Reason: ErrSMTPMailFrom, errlist: []error{err}, isTemp: isTempError(err)}
-			errs = append(errs, message.sendError)
-			if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
-				errs = append(errs, resetSendErr)
-			}
-			continue
-		}
-		failed := false
-		rcptSendErr := &SendError{}
-		rcptSendErr.errlist = make([]error, 0)
-		rcptSendErr.rcpt = make([]string, 0)
-		rcptNotifyOpt := strings.Join(c.dsnrntype, ",")
-		c.smtpClient.SetDSNRcptNotifyOption(rcptNotifyOpt)
-		for _, rcpt := range rcpts {
-			if err = c.smtpClient.Rcpt(rcpt); err != nil {
-				rcptSendErr.Reason = ErrSMTPRcptTo
-				rcptSendErr.errlist = append(rcptSendErr.errlist, err)
-				rcptSendErr.rcpt = append(rcptSendErr.rcpt, rcpt)
-				rcptSendErr.isTemp = isTempError(err)
-				failed = true
-			}
-		}
-		if failed {
-			if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
-				errs = append(errs, resetSendErr)
-			}
-			message.sendError = rcptSendErr
-			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)}
-			errs = append(errs, message.sendError)
-			continue
-		}
-		_, err = message.WriteTo(writer)
-		if err != nil {
-			message.sendError = &SendError{Reason: ErrWriteContent, errlist: []error{err}, isTemp: isTempError(err)}
-			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)}
-			errs = append(errs, message.sendError)
-			continue
-		}
-
-		if err = c.Reset(); err != nil {
-			message.sendError = &SendError{Reason: ErrSMTPReset, errlist: []error{err}, isTemp: isTempError(err)}
-			errs = append(errs, message.sendError)
-			continue
-		}
-		if err = c.checkConn(); err != nil {
-			message.sendError = &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err)}
-			errs = append(errs, message.sendError)
+	for id, message := range messages {
+		if sendErr := c.sendSingleMsg(message); sendErr != nil {
+			messages[id].sendError = sendErr
+			errs = append(errs, sendErr)
 		}
 	}
 
 	return
 }
+
+// sendSingleMsg sends out a single message and returns an error if the transmission/delivery fails.
+// It is invoked by the public Send methods
+func (c *Client) sendSingleMsg(message *Msg) error {
+	if message.encoding == NoEncoding {
+		if ok, _ := c.smtpClient.Extension("8BITMIME"); !ok {
+			return &SendError{Reason: ErrNoUnencoded, isTemp: false}
+		}
+	}
+	from, err := message.GetSender(false)
+	if err != nil {
+		return &SendError{Reason: ErrGetSender, errlist: []error{err}, isTemp: isTempError(err),
+			affectedMsg: message}
+	}
+	rcpts, err := message.GetRecipients()
+	if err != nil {
+		return &SendError{Reason: ErrGetRcpts, errlist: []error{err}, isTemp: isTempError(err),
+			affectedMsg: message}
+	}
+
+	if c.dsn {
+		if c.dsnmrtype != "" {
+			c.smtpClient.SetDSNMailReturnOption(string(c.dsnmrtype))
+		}
+	}
+	if err = c.smtpClient.Mail(from); err != nil {
+		retError := &SendError{Reason: ErrSMTPMailFrom, errlist: []error{err}, isTemp: isTempError(err)}
+		if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
+			retError.errlist = append(retError.errlist, resetSendErr)
+		}
+		return retError
+	}
+	failed := false
+	rcptSendErr := &SendError{}
+	rcptSendErr.errlist = make([]error, 0)
+	rcptSendErr.rcpt = make([]string, 0)
+	rcptNotifyOpt := strings.Join(c.dsnrntype, ",")
+	c.smtpClient.SetDSNRcptNotifyOption(rcptNotifyOpt)
+	for _, rcpt := range rcpts {
+		if err = c.smtpClient.Rcpt(rcpt); err != nil {
+			rcptSendErr.Reason = ErrSMTPRcptTo
+			rcptSendErr.errlist = append(rcptSendErr.errlist, err)
+			rcptSendErr.rcpt = append(rcptSendErr.rcpt, rcpt)
+			rcptSendErr.isTemp = isTempError(err)
+			failed = true
+		}
+	}
+	if failed {
+		if resetSendErr := c.smtpClient.Reset(); resetSendErr != nil {
+			rcptSendErr.errlist = append(rcptSendErr.errlist, resetSendErr)
+		}
+		return rcptSendErr
+	}
+	writer, err := c.smtpClient.Data()
+	if err != nil {
+		return &SendError{Reason: ErrSMTPData, errlist: []error{err}, isTemp: isTempError(err)}
+	}
+	_, err = message.WriteTo(writer)
+	if err != nil {
+		return &SendError{Reason: ErrWriteContent, errlist: []error{err}, isTemp: isTempError(err)}
+	}
+	message.isDelivered = true
+
+	if err = writer.Close(); err != nil {
+		return &SendError{Reason: ErrSMTPDataClose, errlist: []error{err}, isTemp: isTempError(err)}
+	}
+
+	if err = c.Reset(); err != nil {
+		return &SendError{Reason: ErrSMTPReset, errlist: []error{err}, isTemp: isTempError(err)}
+	}
+	if err = c.checkConn(); err != nil {
+		return &SendError{Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err)}
+	}
+	return nil
+}