Split mail sender sub package from mailer service package (#32618)

Move all mail sender related codes into a sub package of
services/mailer. Just move, no code change.
Then we just have dependencies on go-mail package in the new sub
package. We can use other package to replace it because it's
unmaintainable. ref #18664

13 files changed, 491 insertions, 398 deletions

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 8eee32a8c6..ee2c8c0963 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -29,9 +29,8 @@ import (
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/translation"
 	incoming_payload "code.gitea.io/gitea/services/mailer/incoming/payload"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 	"code.gitea.io/gitea/services/mailer/token"
-
-	"gopkg.in/gomail.v2"
 )
 
 const (
@@ -60,7 +59,7 @@ func SendTestMail(email string) error {
 		// No mail service configured
 		return nil
 	}
-	return gomail.Send(Sender, NewMessage(email, "Gitea Test Email!", "Gitea Test Email!").ToMessage())
+	return sender_service.Send(sender, sender_service.NewMessage(email, "Gitea Test Email!", "Gitea Test Email!"))
 }
 
 // sendUserMail sends a mail to the user
@@ -82,7 +81,7 @@ func sendUserMail(language string, u *user_model.User, tpl base.TplName, code, s
 		return
 	}
 
-	msg := NewMessage(u.EmailTo(), subject, content.String())
+	msg := sender_service.NewMessage(u.EmailTo(), subject, content.String())
 	msg.Info = fmt.Sprintf("UID: %d, %s", u.ID, info)
 
 	SendAsync(msg)
@@ -130,7 +129,7 @@ func SendActivateEmailMail(u *user_model.User, email string) {
 		return
 	}
 
-	msg := NewMessage(email, locale.TrString("mail.activate_email"), content.String())
+	msg := sender_service.NewMessage(email, locale.TrString("mail.activate_email"), content.String())
 	msg.Info = fmt.Sprintf("UID: %d, activate email", u.ID)
 
 	SendAsync(msg)
@@ -158,7 +157,7 @@ func SendRegisterNotifyMail(u *user_model.User) {
 		return
 	}
 
-	msg := NewMessage(u.EmailTo(), locale.TrString("mail.register_notify", setting.AppName), content.String())
+	msg := sender_service.NewMessage(u.EmailTo(), locale.TrString("mail.register_notify", setting.AppName), content.String())
 	msg.Info = fmt.Sprintf("UID: %d, registration notify", u.ID)
 
 	SendAsync(msg)
@@ -189,13 +188,13 @@ func SendCollaboratorMail(u, doer *user_model.User, repo *repo_model.Repository)
 		return
 	}
 
-	msg := NewMessage(u.EmailTo(), subject, content.String())
+	msg := sender_service.NewMessage(u.EmailTo(), subject, content.String())
 	msg.Info = fmt.Sprintf("UID: %d, add collaborator", u.ID)
 
 	SendAsync(msg)
 }
 
-func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipients []*user_model.User, fromMention bool, info string) ([]*Message, error) {
+func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipients []*user_model.User, fromMention bool, info string) ([]*sender_service.Message, error) {
 	var (
 		subject string
 		link    string
@@ -304,9 +303,9 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipient
 		return nil, err
 	}
 
-	msgs := make([]*Message, 0, len(recipients))
+	msgs := make([]*sender_service.Message, 0, len(recipients))
 	for _, recipient := range recipients {
-		msg := NewMessageFrom(
+		msg := sender_service.NewMessageFrom(
 			recipient.Email,
 			fromDisplayName(ctx.Doer),
 			setting.MailService.FromEmail,
diff --git a/services/mailer/mail_release.go b/services/mailer/mail_release.go
index af1a7a2662..1d73d77612 100644
--- a/services/mailer/mail_release.go
+++ b/services/mailer/mail_release.go
@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/translation"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 )
 
 const (
@@ -80,11 +81,11 @@ func mailNewRelease(ctx context.Context, lang string, tos []*user_model.User, re
 		return
 	}
 
-	msgs := make([]*Message, 0, len(tos))
+	msgs := make([]*sender_service.Message, 0, len(tos))
 	publisherName := fromDisplayName(rel.Publisher)
 	msgID := generateMessageIDForRelease(rel)
 	for _, to := range tos {
-		msg := NewMessageFrom(to.EmailTo(), publisherName, setting.MailService.FromEmail, subject, mailBody.String())
+		msg := sender_service.NewMessageFrom(to.EmailTo(), publisherName, setting.MailService.FromEmail, subject, mailBody.String())
 		msg.Info = subject
 		msg.SetHeader("Message-ID", msgID)
 		msgs = append(msgs, msg)
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index 7003584786..5f80654bcd 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -13,6 +13,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/translation"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 )
 
 // SendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created
@@ -79,7 +80,7 @@ func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *user_model.U
 	}
 
 	for _, to := range emailTos {
-		msg := NewMessageFrom(to.EmailTo(), fromDisplayName(doer), setting.MailService.FromEmail, subject, content.String())
+		msg := sender_service.NewMessageFrom(to.EmailTo(), fromDisplayName(doer), setting.MailService.FromEmail, subject, content.String())
 		msg.Info = fmt.Sprintf("UID: %d, repository pending transfer notification", newOwner.ID)
 
 		SendAsync(msg)
diff --git a/services/mailer/mail_team_invite.go b/services/mailer/mail_team_invite.go
index ceecefa50f..4f2d5e4ca7 100644
--- a/services/mailer/mail_team_invite.go
+++ b/services/mailer/mail_team_invite.go
@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/translation"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 )
 
 const (
@@ -67,7 +68,7 @@ func MailTeamInvite(ctx context.Context, inviter *user_model.User, team *org_mod
 		return err
 	}
 
-	msg := NewMessage(invite.Email, subject, mailBody.String())
+	msg := sender_service.NewMessage(invite.Email, subject, mailBody.String())
 	msg.Info = subject
 
 	SendAsync(msg)
diff --git a/services/mailer/mail_test.go b/services/mailer/mail_test.go
index 663ffa85ef..42de7599eb 100644
--- a/services/mailer/mail_test.go
+++ b/services/mailer/mail_test.go
@@ -23,6 +23,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/setting"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -167,7 +168,7 @@ func TestTemplateSelection(t *testing.T) {
 	template.Must(bodyTemplates.New("pull/comment").Parse("pull/comment/body"))
 	template.Must(bodyTemplates.New("issue/close").Parse("issue/close/body"))
 
-	expect := func(t *testing.T, msg *Message, expSubject, expBody string) {
+	expect := func(t *testing.T, msg *sender_service.Message, expSubject, expBody string) {
 		subject := msg.ToMessage().GetHeader("Subject")
 		msgbuf := new(bytes.Buffer)
 		_, _ = msg.ToMessage().WriteTo(msgbuf)
@@ -252,7 +253,7 @@ func TestTemplateServices(t *testing.T) {
 		"//Re: //")
 }
 
-func testComposeIssueCommentMessage(t *testing.T, ctx *mailCommentContext, recipients []*user_model.User, fromMention bool, info string) *Message {
+func testComposeIssueCommentMessage(t *testing.T, ctx *mailCommentContext, recipients []*user_model.User, fromMention bool, info string) *sender_service.Message {
 	msgs, err := composeIssueCommentMessages(ctx, "en-US", recipients, fromMention, info)
 	assert.NoError(t, err)
 	assert.Len(t, msgs, 1)
diff --git a/services/mailer/mailer.go b/services/mailer/mailer.go
index 5cb6d03521..bf4b5a43cb 100644
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@@ -5,391 +5,21 @@
 package mailer
 
 import (
-	"bytes"
 	"context"
-	"crypto/tls"
-	"fmt"
-	"hash/fnv"
-	"io"
-	"net"
-	"net/smtp"
-	"os"
-	"os/exec"
-	"strings"
-	"time"
 
-	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/graceful"
 	"code.gitea.io/gitea/modules/log"
-	"code.gitea.io/gitea/modules/process"
 	"code.gitea.io/gitea/modules/queue"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/templates"
+	sender_service "code.gitea.io/gitea/services/mailer/sender"
 	notify_service "code.gitea.io/gitea/services/notify"
-
-	ntlmssp "github.com/Azure/go-ntlmssp"
-	"github.com/jaytaylor/html2text"
-	"gopkg.in/gomail.v2"
 )
 
-// Message mail body and log info
-type Message struct {
-	Info            string // Message information for log purpose.
-	FromAddress     string
-	FromDisplayName string
-	To              string // Use only one recipient to prevent leaking of addresses
-	ReplyTo         string
-	Subject         string
-	Date            time.Time
-	Body            string
-	Headers         map[string][]string
-}
-
-// ToMessage converts a Message to gomail.Message
-func (m *Message) ToMessage() *gomail.Message {
-	msg := gomail.NewMessage()
-	msg.SetAddressHeader("From", m.FromAddress, m.FromDisplayName)
-	msg.SetHeader("To", m.To)
-	if m.ReplyTo != "" {
-		msg.SetHeader("Reply-To", m.ReplyTo)
-	}
-	for header := range m.Headers {
-		msg.SetHeader(header, m.Headers[header]...)
-	}
-
-	if setting.MailService.SubjectPrefix != "" {
-		msg.SetHeader("Subject", setting.MailService.SubjectPrefix+" "+m.Subject)
-	} else {
-		msg.SetHeader("Subject", m.Subject)
-	}
-	msg.SetDateHeader("Date", m.Date)
-	msg.SetHeader("X-Auto-Response-Suppress", "All")
-
-	plainBody, err := html2text.FromString(m.Body)
-	if err != nil || setting.MailService.SendAsPlainText {
-		if strings.Contains(base.TruncateString(m.Body, 100), "<html>") {
-			log.Warn("Mail contains HTML but configured to send as plain text.")
-		}
-		msg.SetBody("text/plain", plainBody)
-	} else {
-		msg.SetBody("text/plain", plainBody)
-		msg.AddAlternative("text/html", m.Body)
-	}
-
-	if len(msg.GetHeader("Message-ID")) == 0 {
-		msg.SetHeader("Message-ID", m.generateAutoMessageID())
-	}
-
-	for k, v := range setting.MailService.OverrideHeader {
-		if len(msg.GetHeader(k)) != 0 {
-			log.Debug("Mailer override header '%s' as per config", k)
-		}
-		msg.SetHeader(k, v...)
-	}
-
-	return msg
-}
-
-// SetHeader adds additional headers to a message
-func (m *Message) SetHeader(field string, value ...string) {
-	m.Headers[field] = value
-}
-
-func (m *Message) generateAutoMessageID() string {
-	dateMs := m.Date.UnixNano() / 1e6
-	h := fnv.New64()
-	if len(m.To) > 0 {
-		_, _ = h.Write([]byte(m.To))
-	}
-	_, _ = h.Write([]byte(m.Subject))
-	_, _ = h.Write([]byte(m.Body))
-	return fmt.Sprintf("<autogen-%d-%016x@%s>", dateMs, h.Sum64(), setting.Domain)
-}
-
-// NewMessageFrom creates new mail message object with custom From header.
-func NewMessageFrom(to, fromDisplayName, fromAddress, subject, body string) *Message {
-	log.Trace("NewMessageFrom (body):\n%s", body)
-
-	return &Message{
-		FromAddress:     fromAddress,
-		FromDisplayName: fromDisplayName,
-		To:              to,
-		Subject:         subject,
-		Date:            time.Now(),
-		Body:            body,
-		Headers:         map[string][]string{},
-	}
-}
-
-// NewMessage creates new mail message object with default From header.
-func NewMessage(to, subject, body string) *Message {
-	return NewMessageFrom(to, setting.MailService.FromName, setting.MailService.FromEmail, subject, body)
-}
-
-type loginAuth struct {
-	username, password string
-}
-
-// LoginAuth SMTP AUTH LOGIN Auth Handler
-func LoginAuth(username, password string) smtp.Auth {
-	return &loginAuth{username, password}
-}
-
-// Start start SMTP login auth
-func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
-	return "LOGIN", []byte{}, nil
-}
-
-// Next next step of SMTP login auth
-func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
-	if more {
-		switch string(fromServer) {
-		case "Username:":
-			return []byte(a.username), nil
-		case "Password:":
-			return []byte(a.password), nil
-		default:
-			return nil, fmt.Errorf("unknown fromServer: %s", string(fromServer))
-		}
-	}
-	return nil, nil
-}
-
-type ntlmAuth struct {
-	username, password, domain string
-	domainNeeded               bool
-}
-
-// NtlmAuth SMTP AUTH NTLM Auth Handler
-func NtlmAuth(username, password string) smtp.Auth {
-	user, domain, domainNeeded := ntlmssp.GetDomain(username)
-	return &ntlmAuth{user, password, domain, domainNeeded}
-}
-
-// Start starts SMTP NTLM Auth
-func (a *ntlmAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
-	negotiateMessage, err := ntlmssp.NewNegotiateMessage(a.domain, "")
-	return "NTLM", negotiateMessage, err
-}
-
-// Next next step of SMTP ntlm auth
-func (a *ntlmAuth) Next(fromServer []byte, more bool) ([]byte, error) {
-	if more {
-		if len(fromServer) == 0 {
-			return nil, fmt.Errorf("ntlm ChallengeMessage is empty")
-		}
-		authenticateMessage, err := ntlmssp.ProcessChallenge(fromServer, a.username, a.password, a.domainNeeded)
-		return authenticateMessage, err
-	}
-	return nil, nil
-}
-
-// Sender SMTP mail sender
-type smtpSender struct{}
-
-// Send send email
-func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
-	opts := setting.MailService
-
-	var network string
-	var address string
-	if opts.Protocol == "smtp+unix" {
-		network = "unix"
-		address = opts.SMTPAddr
-	} else {
-		network = "tcp"
-		address = net.JoinHostPort(opts.SMTPAddr, opts.SMTPPort)
-	}
-
-	conn, err := net.Dial(network, address)
-	if err != nil {
-		return fmt.Errorf("failed to establish network connection to SMTP server: %w", err)
-	}
-	defer conn.Close()
-
-	var tlsconfig *tls.Config
-	if opts.Protocol == "smtps" || opts.Protocol == "smtp+starttls" {
-		tlsconfig = &tls.Config{
-			InsecureSkipVerify: opts.ForceTrustServerCert,
-			ServerName:         opts.SMTPAddr,
-		}
-
-		if opts.UseClientCert {
-			cert, err := tls.LoadX509KeyPair(opts.ClientCertFile, opts.ClientKeyFile)
-			if err != nil {
-				return fmt.Errorf("could not load SMTP client certificate: %w", err)
-			}
-			tlsconfig.Certificates = []tls.Certificate{cert}
-		}
-	}
-
-	if opts.Protocol == "smtps" {
-		conn = tls.Client(conn, tlsconfig)
-	}
-
-	host := "localhost"
-	if opts.Protocol == "smtp+unix" {
-		host = opts.SMTPAddr
-	}
-	client, err := smtp.NewClient(conn, host)
-	if err != nil {
-		return fmt.Errorf("could not initiate SMTP session: %w", err)
-	}
-
-	if opts.EnableHelo {
-		hostname := opts.HeloHostname
-		if len(hostname) == 0 {
-			hostname, err = os.Hostname()
-			if err != nil {
-				return fmt.Errorf("could not retrieve system hostname: %w", err)
-			}
-		}
-
-		if err = client.Hello(hostname); err != nil {
-			return fmt.Errorf("failed to issue HELO command: %w", err)
-		}
-	}
-
-	if opts.Protocol == "smtp+starttls" {
-		hasStartTLS, _ := client.Extension("STARTTLS")
-		if hasStartTLS {
-			if err = client.StartTLS(tlsconfig); err != nil {
-				return fmt.Errorf("failed to start TLS connection: %w", err)
-			}
-		} else {
-			log.Warn("StartTLS requested, but SMTP server does not support it; falling back to regular SMTP")
-		}
-	}
-
-	canAuth, options := client.Extension("AUTH")
-	if len(opts.User) > 0 {
-		if !canAuth {
-			return fmt.Errorf("SMTP server does not support AUTH, but credentials provided")
-		}
-
-		var auth smtp.Auth
-
-		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)
-		} else if strings.Contains(options, "LOGIN") {
-			// Patch for AUTH LOGIN
-			auth = LoginAuth(opts.User, opts.Passwd)
-		} else if strings.Contains(options, "NTLM") {
-			auth = NtlmAuth(opts.User, opts.Passwd)
-		}
-
-		if auth != nil {
-			if err = client.Auth(auth); err != nil {
-				return fmt.Errorf("failed to authenticate SMTP: %w", err)
-			}
-		}
-	}
-
-	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(from); err != nil {
-			return fmt.Errorf("failed to issue MAIL command: %w", err)
-		}
-	}
-
-	for _, rec := range to {
-		if err = client.Rcpt(rec); err != nil {
-			return fmt.Errorf("failed to issue RCPT command: %w", err)
-		}
-	}
-
-	w, err := client.Data()
-	if err != nil {
-		return fmt.Errorf("failed to issue DATA command: %w", err)
-	} else if _, err = msg.WriteTo(w); err != nil {
-		return fmt.Errorf("SMTP write failed: %w", err)
-	} else if err = w.Close(); err != nil {
-		return fmt.Errorf("SMTP close failed: %w", err)
-	}
-
-	return client.Quit()
-}
-
-// Sender sendmail mail sender
-type sendmailSender struct{}
-
-// Send send email
-func (s *sendmailSender) Send(from string, to []string, msg io.WriterTo) error {
-	var err error
-	var closeError error
-	var waitError error
-
-	envelopeFrom := from
-	if setting.MailService.OverrideEnvelopeFrom {
-		envelopeFrom = setting.MailService.EnvelopeFrom
-	}
-
-	args := []string{"-f", envelopeFrom, "-i"}
-	args = append(args, setting.MailService.SendmailArgs...)
-	args = append(args, to...)
-	log.Trace("Sending with: %s %v", setting.MailService.SendmailPath, args)
-
-	desc := fmt.Sprintf("SendMail: %s %v", setting.MailService.SendmailPath, args)
-
-	ctx, _, finished := process.GetManager().AddContextTimeout(graceful.GetManager().HammerContext(), setting.MailService.SendmailTimeout, desc)
-	defer finished()
-
-	cmd := exec.CommandContext(ctx, setting.MailService.SendmailPath, args...)
-	pipe, err := cmd.StdinPipe()
-	if err != nil {
-		return err
-	}
-	process.SetSysProcAttribute(cmd)
-
-	if err = cmd.Start(); err != nil {
-		_ = pipe.Close()
-		return err
-	}
-
-	if setting.MailService.SendmailConvertCRLF {
-		buf := &strings.Builder{}
-		_, err = msg.WriteTo(buf)
-		if err == nil {
-			_, err = strings.NewReplacer("\r\n", "\n").WriteString(pipe, buf.String())
-		}
-	} else {
-		_, err = msg.WriteTo(pipe)
-	}
-
-	// we MUST close the pipe or sendmail will hang waiting for more of the message
-	// Also we should wait on our sendmail command even if something fails
-	closeError = pipe.Close()
-	waitError = cmd.Wait()
-	if err != nil {
-		return err
-	} else if closeError != nil {
-		return closeError
-	}
-	return waitError
-}
-
-// Sender sendmail mail sender
-type dummySender struct{}
-
-// Send send email
-func (s *dummySender) Send(from string, to []string, msg io.WriterTo) error {
-	buf := bytes.Buffer{}
-	if _, err := msg.WriteTo(&buf); err != nil {
-		return err
-	}
-	log.Debug("Mail From: %s To: %v Body: %s", from, to, buf.String())
-	return nil
-}
-
-var mailQueue *queue.WorkerPoolQueue[*Message]
+var mailQueue *queue.WorkerPoolQueue[*sender_service.Message]
 
-// Sender sender for sending mail synchronously
-var Sender gomail.Sender
+// sender sender for sending mail synchronously
+var sender sender_service.Sender
 
 // NewContext start mail queue service
 func NewContext(ctx context.Context) {
@@ -406,20 +36,20 @@ func NewContext(ctx context.Context) {
 
 	switch setting.MailService.Protocol {
 	case "sendmail":
-		Sender = &sendmailSender{}
+		sender = &sender_service.SendmailSender{}
 	case "dummy":
-		Sender = &dummySender{}
+		sender = &sender_service.DummySender{}
 	default:
-		Sender = &smtpSender{}
+		sender = &sender_service.SMTPSender{}
 	}
 
 	subjectTemplates, bodyTemplates = templates.Mailer(ctx)
 
-	mailQueue = queue.CreateSimpleQueue(graceful.GetManager().ShutdownContext(), "mail", func(items ...*Message) []*Message {
+	mailQueue = queue.CreateSimpleQueue(graceful.GetManager().ShutdownContext(), "mail", func(items ...*sender_service.Message) []*sender_service.Message {
 		for _, msg := range items {
 			gomailMsg := msg.ToMessage()
 			log.Trace("New e-mail sending request %s: %s", gomailMsg.GetHeader("To"), msg.Info)
-			if err := gomail.Send(Sender, gomailMsg); err != nil {
+			if err := sender_service.Send(sender, msg); err != nil {
 				log.Error("Failed to send emails %s: %s - %v", gomailMsg.GetHeader("To"), msg.Info, err)
 			} else {
 				log.Trace("E-mails sent %s: %s", gomailMsg.GetHeader("To"), msg.Info)
@@ -436,7 +66,7 @@ func NewContext(ctx context.Context) {
 // SendAsync send emails asynchronously (make it mockable)
 var SendAsync = sendAsync
 
-func sendAsync(msgs ...*Message) {
+func sendAsync(msgs ...*sender_service.Message) {
 	if setting.MailService == nil {
 		log.Error("Mailer: SendAsync is being invoked but mail service hasn't been initialized")
 		return
diff --git a/services/mailer/sender/dummy.go b/services/mailer/sender/dummy.go
new file mode 100644
index 0000000000..dd5f14abec
--- /dev/null
+++ b/services/mailer/sender/dummy.go
@@ -0,0 +1,26 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"bytes"
+	"io"
+
+	"code.gitea.io/gitea/modules/log"
+)
+
+// DummySender Sender sendmail mail sender
+type DummySender struct{}
+
+var _ Sender = &DummySender{}
+
+// Send send email
+func (s *DummySender) Send(from string, to []string, msg io.WriterTo) error {
+	buf := bytes.Buffer{}
+	if _, err := msg.WriteTo(&buf); err != nil {
+		return err
+	}
+	log.Debug("Mail From: %s To: %v Body: %s", from, to, buf.String())
+	return nil
+}
diff --git a/services/mailer/sender/message.go b/services/mailer/sender/message.go
new file mode 100644
index 0000000000..a3255692f0
--- /dev/null
+++ b/services/mailer/sender/message.go
@@ -0,0 +1,112 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"fmt"
+	"hash/fnv"
+	"strings"
+	"time"
+
+	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/jaytaylor/html2text"
+	"gopkg.in/gomail.v2"
+)
+
+// Message mail body and log info
+type Message struct {
+	Info            string // Message information for log purpose.
+	FromAddress     string
+	FromDisplayName string
+	To              string // Use only one recipient to prevent leaking of addresses
+	ReplyTo         string
+	Subject         string
+	Date            time.Time
+	Body            string
+	Headers         map[string][]string
+}
+
+// ToMessage converts a Message to gomail.Message
+func (m *Message) ToMessage() *gomail.Message {
+	msg := gomail.NewMessage()
+	msg.SetAddressHeader("From", m.FromAddress, m.FromDisplayName)
+	msg.SetHeader("To", m.To)
+	if m.ReplyTo != "" {
+		msg.SetHeader("Reply-To", m.ReplyTo)
+	}
+	for header := range m.Headers {
+		msg.SetHeader(header, m.Headers[header]...)
+	}
+
+	if setting.MailService.SubjectPrefix != "" {
+		msg.SetHeader("Subject", setting.MailService.SubjectPrefix+" "+m.Subject)
+	} else {
+		msg.SetHeader("Subject", m.Subject)
+	}
+	msg.SetDateHeader("Date", m.Date)
+	msg.SetHeader("X-Auto-Response-Suppress", "All")
+
+	plainBody, err := html2text.FromString(m.Body)
+	if err != nil || setting.MailService.SendAsPlainText {
+		if strings.Contains(base.TruncateString(m.Body, 100), "<html>") {
+			log.Warn("Mail contains HTML but configured to send as plain text.")
+		}
+		msg.SetBody("text/plain", plainBody)
+	} else {
+		msg.SetBody("text/plain", plainBody)
+		msg.AddAlternative("text/html", m.Body)
+	}
+
+	if len(msg.GetHeader("Message-ID")) == 0 {
+		msg.SetHeader("Message-ID", m.generateAutoMessageID())
+	}
+
+	for k, v := range setting.MailService.OverrideHeader {
+		if len(msg.GetHeader(k)) != 0 {
+			log.Debug("Mailer override header '%s' as per config", k)
+		}
+		msg.SetHeader(k, v...)
+	}
+
+	return msg
+}
+
+// SetHeader adds additional headers to a message
+func (m *Message) SetHeader(field string, value ...string) {
+	m.Headers[field] = value
+}
+
+func (m *Message) generateAutoMessageID() string {
+	dateMs := m.Date.UnixNano() / 1e6
+	h := fnv.New64()
+	if len(m.To) > 0 {
+		_, _ = h.Write([]byte(m.To))
+	}
+	_, _ = h.Write([]byte(m.Subject))
+	_, _ = h.Write([]byte(m.Body))
+	return fmt.Sprintf("<autogen-%d-%016x@%s>", dateMs, h.Sum64(), setting.Domain)
+}
+
+// NewMessageFrom creates new mail message object with custom From header.
+func NewMessageFrom(to, fromDisplayName, fromAddress, subject, body string) *Message {
+	log.Trace("NewMessageFrom (body):\n%s", body)
+
+	return &Message{
+		FromAddress:     fromAddress,
+		FromDisplayName: fromDisplayName,
+		To:              to,
+		Subject:         subject,
+		Date:            time.Now(),
+		Body:            body,
+		Headers:         map[string][]string{},
+	}
+}
+
+// NewMessage creates new mail message object with default From header.
+func NewMessage(to, subject, body string) *Message {
+	return NewMessageFrom(to, setting.MailService.FromName, setting.MailService.FromEmail, subject, body)
+}
diff --git a/services/mailer/mailer_test.go b/services/mailer/sender/message_test.go
index 6d7c44f40c..d47052685e 100644
--- a/services/mailer/mailer_test.go
+++ b/services/mailer/sender/message_test.go
@@ -1,7 +1,7 @@
-// Copyright 2021 The Gogs Authors. All rights reserved.
+// Copyright 2024 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
-package mailer
+package sender
 
 import (
 	"strings"
diff --git a/services/mailer/sender/sender.go b/services/mailer/sender/sender.go
new file mode 100644
index 0000000000..bf317aa846
--- /dev/null
+++ b/services/mailer/sender/sender.go
@@ -0,0 +1,27 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"gopkg.in/gomail.v2"
+)
+
+type Sender gomail.Sender
+
+var Send = send
+
+func send(sender Sender, msgs ...*Message) error {
+	if setting.MailService == nil {
+		log.Error("Mailer: Send is being invoked but mail service hasn't been initialized")
+		return nil
+	}
+	goMsgs := []*gomail.Message{}
+	for _, msg := range msgs {
+		goMsgs = append(goMsgs, msg.ToMessage())
+	}
+	return gomail.Send(sender, goMsgs...)
+}
diff --git a/services/mailer/sender/sendmail.go b/services/mailer/sender/sendmail.go
new file mode 100644
index 0000000000..64c7f8f081
--- /dev/null
+++ b/services/mailer/sender/sendmail.go
@@ -0,0 +1,76 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+
+	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/process"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// SendmailSender Sender sendmail mail sender
+type SendmailSender struct{}
+
+var _ Sender = &SendmailSender{}
+
+// Send send email
+func (s *SendmailSender) Send(from string, to []string, msg io.WriterTo) error {
+	var err error
+	var closeError error
+	var waitError error
+
+	envelopeFrom := from
+	if setting.MailService.OverrideEnvelopeFrom {
+		envelopeFrom = setting.MailService.EnvelopeFrom
+	}
+
+	args := []string{"-f", envelopeFrom, "-i"}
+	args = append(args, setting.MailService.SendmailArgs...)
+	args = append(args, to...)
+	log.Trace("Sending with: %s %v", setting.MailService.SendmailPath, args)
+
+	desc := fmt.Sprintf("SendMail: %s %v", setting.MailService.SendmailPath, args)
+
+	ctx, _, finished := process.GetManager().AddContextTimeout(graceful.GetManager().HammerContext(), setting.MailService.SendmailTimeout, desc)
+	defer finished()
+
+	cmd := exec.CommandContext(ctx, setting.MailService.SendmailPath, args...)
+	pipe, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+	process.SetSysProcAttribute(cmd)
+
+	if err = cmd.Start(); err != nil {
+		_ = pipe.Close()
+		return err
+	}
+
+	if setting.MailService.SendmailConvertCRLF {
+		buf := &strings.Builder{}
+		_, err = msg.WriteTo(buf)
+		if err == nil {
+			_, err = strings.NewReplacer("\r\n", "\n").WriteString(pipe, buf.String())
+		}
+	} else {
+		_, err = msg.WriteTo(pipe)
+	}
+
+	// we MUST close the pipe or sendmail will hang waiting for more of the message
+	// Also we should wait on our sendmail command even if something fails
+	closeError = pipe.Close()
+	waitError = cmd.Wait()
+	if err != nil {
+		return err
+	} else if closeError != nil {
+		return closeError
+	}
+	return waitError
+}
diff --git a/services/mailer/sender/smtp.go b/services/mailer/sender/smtp.go
new file mode 100644
index 0000000000..ab49b7e5f8
--- /dev/null
+++ b/services/mailer/sender/smtp.go
@@ -0,0 +1,150 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"crypto/tls"
+	"fmt"
+	"io"
+	"net"
+	"net/smtp"
+	"os"
+	"strings"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// SMTPSender Sender SMTP mail sender
+type SMTPSender struct{}
+
+var _ Sender = &SMTPSender{}
+
+// Send send email
+func (s *SMTPSender) Send(from string, to []string, msg io.WriterTo) error {
+	opts := setting.MailService
+
+	var network string
+	var address string
+	if opts.Protocol == "smtp+unix" {
+		network = "unix"
+		address = opts.SMTPAddr
+	} else {
+		network = "tcp"
+		address = net.JoinHostPort(opts.SMTPAddr, opts.SMTPPort)
+	}
+
+	conn, err := net.Dial(network, address)
+	if err != nil {
+		return fmt.Errorf("failed to establish network connection to SMTP server: %w", err)
+	}
+	defer conn.Close()
+
+	var tlsconfig *tls.Config
+	if opts.Protocol == "smtps" || opts.Protocol == "smtp+starttls" {
+		tlsconfig = &tls.Config{
+			InsecureSkipVerify: opts.ForceTrustServerCert,
+			ServerName:         opts.SMTPAddr,
+		}
+
+		if opts.UseClientCert {
+			cert, err := tls.LoadX509KeyPair(opts.ClientCertFile, opts.ClientKeyFile)
+			if err != nil {
+				return fmt.Errorf("could not load SMTP client certificate: %w", err)
+			}
+			tlsconfig.Certificates = []tls.Certificate{cert}
+		}
+	}
+
+	if opts.Protocol == "smtps" {
+		conn = tls.Client(conn, tlsconfig)
+	}
+
+	host := "localhost"
+	if opts.Protocol == "smtp+unix" {
+		host = opts.SMTPAddr
+	}
+	client, err := smtp.NewClient(conn, host)
+	if err != nil {
+		return fmt.Errorf("could not initiate SMTP session: %w", err)
+	}
+
+	if opts.EnableHelo {
+		hostname := opts.HeloHostname
+		if len(hostname) == 0 {
+			hostname, err = os.Hostname()
+			if err != nil {
+				return fmt.Errorf("could not retrieve system hostname: %w", err)
+			}
+		}
+
+		if err = client.Hello(hostname); err != nil {
+			return fmt.Errorf("failed to issue HELO command: %w", err)
+		}
+	}
+
+	if opts.Protocol == "smtp+starttls" {
+		hasStartTLS, _ := client.Extension("STARTTLS")
+		if hasStartTLS {
+			if err = client.StartTLS(tlsconfig); err != nil {
+				return fmt.Errorf("failed to start TLS connection: %w", err)
+			}
+		} else {
+			log.Warn("StartTLS requested, but SMTP server does not support it; falling back to regular SMTP")
+		}
+	}
+
+	canAuth, options := client.Extension("AUTH")
+	if len(opts.User) > 0 {
+		if !canAuth {
+			return fmt.Errorf("SMTP server does not support AUTH, but credentials provided")
+		}
+
+		var auth smtp.Auth
+
+		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)
+		} else if strings.Contains(options, "LOGIN") {
+			// Patch for AUTH LOGIN
+			auth = LoginAuth(opts.User, opts.Passwd)
+		} else if strings.Contains(options, "NTLM") {
+			auth = NtlmAuth(opts.User, opts.Passwd)
+		}
+
+		if auth != nil {
+			if err = client.Auth(auth); err != nil {
+				return fmt.Errorf("failed to authenticate SMTP: %w", err)
+			}
+		}
+	}
+
+	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(from); err != nil {
+			return fmt.Errorf("failed to issue MAIL command: %w", err)
+		}
+	}
+
+	for _, rec := range to {
+		if err = client.Rcpt(rec); err != nil {
+			return fmt.Errorf("failed to issue RCPT command: %w", err)
+		}
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		return fmt.Errorf("failed to issue DATA command: %w", err)
+	} else if _, err = msg.WriteTo(w); err != nil {
+		return fmt.Errorf("SMTP write failed: %w", err)
+	} else if err = w.Close(); err != nil {
+		return fmt.Errorf("SMTP close failed: %w", err)
+	}
+
+	return client.Quit()
+}
diff --git a/services/mailer/sender/smtp_auth.go b/services/mailer/sender/smtp_auth.go
new file mode 100644
index 0000000000..df65498a5a
--- /dev/null
+++ b/services/mailer/sender/smtp_auth.go
@@ -0,0 +1,69 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sender
+
+import (
+	"fmt"
+	"net/smtp"
+
+	"github.com/Azure/go-ntlmssp"
+)
+
+type loginAuth struct {
+	username, password string
+}
+
+// LoginAuth SMTP AUTH LOGIN Auth Handler
+func LoginAuth(username, password string) smtp.Auth {
+	return &loginAuth{username, password}
+}
+
+// Start start SMTP login auth
+func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
+	return "LOGIN", []byte{}, nil
+}
+
+// Next next step of SMTP login auth
+func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		switch string(fromServer) {
+		case "Username:":
+			return []byte(a.username), nil
+		case "Password:":
+			return []byte(a.password), nil
+		default:
+			return nil, fmt.Errorf("unknown fromServer: %s", string(fromServer))
+		}
+	}
+	return nil, nil
+}
+
+type ntlmAuth struct {
+	username, password, domain string
+	domainNeeded               bool
+}
+
+// NtlmAuth SMTP AUTH NTLM Auth Handler
+func NtlmAuth(username, password string) smtp.Auth {
+	user, domain, domainNeeded := ntlmssp.GetDomain(username)
+	return &ntlmAuth{user, password, domain, domainNeeded}
+}
+
+// Start starts SMTP NTLM Auth
+func (a *ntlmAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
+	negotiateMessage, err := ntlmssp.NewNegotiateMessage(a.domain, "")
+	return "NTLM", negotiateMessage, err
+}
+
+// Next next step of SMTP ntlm auth
+func (a *ntlmAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		if len(fromServer) == 0 {
+			return nil, fmt.Errorf("ntlm ChallengeMessage is empty")
+		}
+		authenticateMessage, err := ntlmssp.ProcessChallenge(fromServer, a.username, a.password, a.domainNeeded)
+		return authenticateMessage, err
+	}
+	return nil, nil
+}