Use Golang net/smtp instead of gomail's smtp to send email (#36055)

Replace #36032
Fix #36030

This PR use `net/smtp` instead of gomail's smtp. Now
github.com/wneessen/go-mail will be used only for generating email
message body.

---------

Co-authored-by: Giteabot <teabot@gitea.io>

services/mailer/sender/sendmail.go

@@ -33,7 +33,13 @@ func (s *SendmailSender) Send(from string, to []string, msg io.WriterTo) error {
 
 	args := []string{"-f", envelopeFrom, "-i"}
 	args = append(args, setting.MailService.SendmailArgs...)
-	args = append(args, to...)
+	for _, recipient := range to {
+		smtpTo, err := sanitizeEmailAddress(recipient)
+		if err != nil {
+			return fmt.Errorf("invalid recipient address %q: %w", recipient, err)
+		}
+		args = append(args, smtpTo)
+	}
 	log.Trace("Sending with: %s %v", setting.MailService.SendmailPath, args)
 
 	desc := fmt.Sprintf("SendMail: %s %v", setting.MailService.SendmailPath, args)

services/mailer/sender/smtp.go

@@ -9,13 +9,13 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/mail"
+	"net/smtp"
 	"os"
 	"strings"
 
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
-
-	"github.com/wneessen/go-mail/smtp"
 )
 
 // SMTPSender Sender SMTP mail sender
@@ -108,7 +108,7 @@ func (s *SMTPSender) Send(from string, to []string, msg io.WriterTo) error {
 		if strings.Contains(options, "CRAM-MD5") {
 			auth = smtp.CRAMMD5Auth(opts.User, opts.Passwd)
 		} else if strings.Contains(options, "PLAIN") {
-			auth = smtp.PlainAuth("", opts.User, opts.Passwd, host, false)
+			auth = smtp.PlainAuth("", opts.User, opts.Passwd, host)
 		} else if strings.Contains(options, "LOGIN") {
 			// Patch for AUTH LOGIN
 			auth = LoginAuth(opts.User, opts.Passwd)
@@ -123,18 +123,24 @@ func (s *SMTPSender) Send(from string, to []string, msg io.WriterTo) error {
 		}
 	}
 
-	if opts.OverrideEnvelopeFrom {
-		if err = client.Mail(opts.EnvelopeFrom); err != nil {
-			return fmt.Errorf("failed to issue MAIL command: %w", err)
-		}
-	} else {
-		if err = client.Mail(fmt.Sprintf("<%s>", from)); err != nil {
-			return fmt.Errorf("failed to issue MAIL command: %w", err)
-		}
+	fromAddr := from
+	if opts.OverrideEnvelopeFrom && opts.EnvelopeFrom != "" {
+		fromAddr = opts.EnvelopeFrom
+	}
+	smtpFrom, err := sanitizeEmailAddress(fromAddr)
+	if err != nil {
+		return fmt.Errorf("invalid envelope from address: %w", err)
+	}
+	if err = client.Mail(smtpFrom); err != nil {
+		return fmt.Errorf("failed to issue MAIL command: %w", err)
 	}
 
 	for _, rec := range to {
-		if err = client.Rcpt(rec); err != nil {
+		smtpTo, err := sanitizeEmailAddress(rec)
+		if err != nil {
+			return fmt.Errorf("invalid recipient address %q: %w", rec, err)
+		}
+		if err = client.Rcpt(smtpTo); err != nil {
 			return fmt.Errorf("failed to issue RCPT command: %w", err)
 		}
 	}
@@ -155,3 +161,11 @@ func (s *SMTPSender) Send(from string, to []string, msg io.WriterTo) error {
 
 	return nil
 }
+
+func sanitizeEmailAddress(raw string) (string, error) {
+	addr, err := mail.ParseAddress(strings.TrimSpace(strings.Trim(raw, "<>")))
+	if err != nil {
+		return "", err
+	}
+	return addr.Address, nil
+}

services/mailer/sender/smtp_auth.go

@@ -6,9 +6,9 @@ package sender
 import (
 	"errors"
 	"fmt"
+	"net/smtp"
 
 	"github.com/Azure/go-ntlmssp"
-	"github.com/wneessen/go-mail/smtp"
 )
 
 type loginAuth struct {

services/mailer/sender/smtp_test.go

@@ -0,0 +1,30 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import "testing"
+
+func TestSanitizeEmailAddress(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+		hasError bool
+	}{
+		{"abc@gitea.com", "abc@gitea.com", false},
+		{"<abc@gitea.com>", "abc@gitea.com", false},
+		{"ssss.com", "", true},
+		{"<invalid-email>", "", true},
+	}
+
+	for _, tt := range tests {
+		result, err := sanitizeEmailAddress(tt.input)
+		if (err != nil) != tt.hasError {
+			t.Errorf("sanitizeEmailAddress(%q) unexpected error status: got %v, want error: %v", tt.input, err != nil, tt.hasError)
+			continue
+		}
+		if result != tt.expected {
+			t.Errorf("sanitizeEmailAddress(%q) = %q; want %q", tt.input, result, tt.expected)
+		}
+	}
+}