Rework mailer settings (#18982)

* `PROTOCOL`: can be smtp, smtps, smtp+startls, smtp+unix, sendmail, dummy * `SMTP_ADDR`: domain for SMTP, or path to unix socket * `SMTP_PORT`: port for SMTP; defaults to 25 for `smtp`, 465 for `smtps`, and 587 for `smtp+startls` * `ENABLE_HELO`, `HELO_HOSTNAME`: reverse `DISABLE_HELO` to `ENABLE_HELO`; default to false + system hostname * `FORCE_TRUST_SERVER_CERT`: replace the unclear `SKIP_VERIFY` * `CLIENT_CERT_FILE`, `CLIENT_KEY_FILE`, `USE_CLIENT_CERT`: clarify client certificates here Co-authored-by: wxiaoguang <wxiaoguang@gmail.com> Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
2024-12-27 07:56:13 +00:00 · 2022-08-02 01:24:18 -04:00 · 2022-08-02 01:24:18 -04:00 · 036dd8a788
commit 036dd8a788
parent ae3b88bef3
14 changed files with 300 additions and 158 deletions
--- a/cmd/admin.go
+++ b/cmd/admin.go
@ -414,9 +414,9 @@ var (
 			Usage: "SMTP Authentication Type (PLAIN/LOGIN/CRAM-MD5) default PLAIN",
 		},
 		cli.StringFlag{
-			Name:  "host",
+			Name:  "addr",
 			Value: "",
-			Usage: "SMTP Host",
+			Usage: "SMTP Addr",
 		},
 		cli.IntFlag{
 			Name:  "port",
@ -956,8 +956,8 @@ func parseSMTPConfig(c *cli.Context, conf *smtp.Source) error {
 		}
 		conf.Auth = c.String("auth-type")
 	}
-	if c.IsSet("host") {
-		conf.Host = c.String("host")
+	if c.IsSet("addr") {
+		conf.Addr = c.String("addr")
 	}
 	if c.IsSet("port") {
 		conf.Port = c.Int("port")
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@ -1503,30 +1503,42 @@ ROUTER = console
 ;; Prefix displayed before subject in mail
 ;SUBJECT_PREFIX =
 ;;
-;; Mail server
-;; Gmail: smtp.gmail.com:587
-;; QQ: smtp.qq.com:465
-;; As per RFC 8314 using Implicit TLS/SMTPS on port 465 (if supported) is recommended,
-;; otherwise STARTTLS on port 587 should be used.
-;HOST =
+;; Mail server protocol. One of "smtp", "smtps", "smtp+startls", "smtp+unix", "sendmail", "dummy".
+;; - sendmail: use the operating system's `sendmail` command instead of SMTP. This is common on Linux systems.
+;; - dummy: send email messages to the log as a testing phase.
+;; If your provider does not explicitly say which protocol it uses but does provide a port,
+;; you can set SMTP_PORT instead and this will be inferred.
+;; (Before 1.18, this was controlled via MAILER_TYPE and IS_TLS_ENABLED.)
+;PROTOCOL =
 ;;
-;; Disable HELO operation when hostnames are different.
-;DISABLE_HELO =
+;; Mail server address, e.g. smtp.gmail.com.
+;; For smtp+unix, this should be a path to a unix socket instead.
+;; (Before 1.18, this was combined with SMTP_PORT as HOST.)
+;SMTP_ADDR =
 ;;
-;; Custom hostname for HELO operation, if no value is provided, one is retrieved from system.
+;; Mail server port. Common ports are:
+;;   25:  insecure SMTP
+;;   465: SMTP Secure
+;;   587: StartTLS
+;; If no protocol is specified, it will be inferred by this setting.
+;; (Before 1.18, this was combined with SMTP_ADDR as HOST.)
+;SMTP_PORT =
+;;
+;; Enable HELO operation. Defaults to true.
+;ENABLE_HELO = true
+;;
+;; Custom hostname for HELO operation.
+;; If no value is provided, one is retrieved from system.
 ;HELO_HOSTNAME =
 ;;
-;; Whether or not to skip verification of certificates; `true` to disable verification. This option is unsafe. Consider adding the certificate to the system trust store instead.
-;SKIP_VERIFY = false
+;; If set to `true`, completely ignores server certificate validation errors.
+;; This option is unsafe. Consider adding the certificate to the system trust store instead.
+;FORCE_TRUST_SERVER_CERT = false
 ;;
-;; Use client certificate
-;USE_CERTIFICATE = false
-;CERT_FILE = custom/mailer/cert.pem
-;KEY_FILE = custom/mailer/key.pem
-;;
-;; Should SMTP connect with TLS, (if port ends with 465 TLS will always be used.)
-;; If this is false but STARTTLS is supported the connection will be upgraded to TLS opportunistically.
-;IS_TLS_ENABLED = false
+;; Use client certificate in connection.
+;USE_CLIENT_CERT = false
+;CLIENT_CERT_FILE = custom/mailer/cert.pem
+;CLIENT_KEY_FILE = custom/mailer/key.pem
 ;;
 ;; Mail from address, RFC 5322. This can be just an email address, or the `"Name" <email@example.com>` format
 ;FROM =
@ -1534,19 +1546,15 @@ ROUTER = console
 ;; Sometimes it is helpful to use a different address on the envelope. Set this to use ENVELOPE_FROM as the from on the envelope. Set to `<>` to send an empty address.
 ;ENVELOPE_FROM =
 ;;
-;; Mailer user name and password
-;; Please Note: Authentication is only supported when the SMTP server communication is encrypted with TLS (this can be via STARTTLS) or `HOST=localhost`.
+;; Mailer user name and password, if required by provider.
 ;USER =
 ;;
 ;; Use PASSWD = `your password` for quoting if you use special characters in the password.
 ;PASSWD =
 ;;
-;; Send mails as plain text
+;; Send mails only in plain text, without HTML alternative
 ;SEND_AS_PLAIN_TEXT = false
 ;;
-;; Set Mailer Type (either SMTP, sendmail or dummy to just send to the log)
-;MAILER_TYPE = smtp
-;;
 ;; Specify an alternative sendmail binary
 ;SENDMAIL_PATH = sendmail
 ;;
--- a/docs/content/doc/advanced/config-cheat-sheet.en-us.md
+++ b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
@ -647,41 +647,35 @@ Define allowed algorithms and their minimum key length (use -1 to disable a type
 ## Mailer (`mailer`)

 - `ENABLED`: **false**: Enable to use a mail service.
- `DISABLE_HELO`: **\<empty\>**: Disable HELO operation.
- `HELO_HOSTNAME`: **\<empty\>**: Custom hostname for HELO operation.
- `HOST`: **\<empty\>**: SMTP mail host address and port (example: smtp.gitea.io:587).
-  - As per RFC 8314, if supported, Implicit TLS/SMTPS on port 465 is recommended, otherwise opportunistic TLS via STARTTLS on port 587 should be used.
- `IS_TLS_ENABLED` :  **false** : Forcibly use TLS to connect even if not on a default SMTPS port.
-  - Note, if the port ends with `465` Implicit TLS/SMTPS/SMTP over TLS will be used despite this setting.
-  - Otherwise if `IS_TLS_ENABLED=false` and the server supports `STARTTLS` this will be used. Thus if `STARTTLS` is preferred you should set `IS_TLS_ENABLED=false`.
- `FROM`: **\<empty\>**: Mail from address, RFC 5322. This can be just an email address, or
-   the "Name" \<email@example.com\> format.
- `ENVELOPE_FROM`: **\<empty\>**: Address set as the From address on the SMTP mail envelope. Set to `<>` to send an empty address.
+- `PROTOCOL`: **\<empty\>**: Mail server protocol. One of "smtp", "smtps", "smtp+startls", "smtp+unix", "sendmail", "dummy". _Before 1.18, this was inferred from a combination of `MAILER_TYPE` and `IS_TLS_ENABLED`._
+  - SMTP family, if your provider does not explicitly say which protocol it uses but does provide a port, you can set SMTP_PORT instead and this will be inferred.
+  - **sendmail** Use the operating system's `sendmail` command instead of SMTP. This is common on Linux systems.
+  - **dummy** Send email messages to the log as a testing phase.
+  - Note that enabling sendmail will ignore all other `mailer` settings except `ENABLED`, `FROM`, `SUBJECT_PREFIX` and `SENDMAIL_PATH`.
+  - Enabling dummy will ignore all settings except `ENABLED`, `SUBJECT_PREFIX` and `FROM`.
+- `SMTP_ADDR`: **\<empty\>**: Mail server address. e.g. smtp.gmail.com. For smtp+unix, this should be a path to a unix socket instead. _Before 1.18, this was combined with `SMTP_PORT` under the name `HOST`._
+- `SMTP_PORT`: **\<empty\>**: Mail server port. If no protocol is specified, it will be inferred by this setting. Common ports are listed below. _Before 1.18, this was combined with `SMTP_ADDR` under the name `HOST`._
+  - 25:  insecure SMTP
+  - 465: SMTP Secure
+  - 587: StartTLS
+- `USE_CLIENT_CERT`: **false**: Use client certificate for TLS/SSL.
+- `CLIENT_CERT_FILE`: **custom/mailer/cert.pem**: Client certificate file.
+- `CLIENT_KEY_FILE`: **custom/mailer/key.pem**: Client key file.
+- `FORCE_TRUST_SERVER_CERT`: **false**: If set to `true`, completely ignores server certificate validation errors. This option is unsafe. Consider adding the certificate to the system trust store instead.
 - `USER`: **\<empty\>**: Username of mailing user (usually the sender's e-mail address).
 - `PASSWD`: **\<empty\>**: Password of mailing user.  Use \`your password\` for quoting if you use special characters in the password.
-  - Please note: authentication is only supported when the SMTP server communication is encrypted with TLS (this can be via `STARTTLS`) or `HOST=localhost`. See [Email Setup]({{< relref "doc/usage/email-setup.en-us.md" >}}) for more information.
- `SEND_AS_PLAIN_TEXT`: **false**: Send mails as plain text.
- `SKIP_VERIFY`: **false**: Whether or not to skip verification of certificates; `true` to disable verification.
-  - **Warning:** This option is unsafe. Consider adding the certificate to the system trust store instead.
-  - **Note:** Gitea only supports SMTP with STARTTLS.
- `USE_CERTIFICATE`: **false**: Use client certificate.
- `CERT_FILE`: **custom/mailer/cert.pem**
- `KEY_FILE`: **custom/mailer/key.pem**
+  - Please note: authentication is only supported when the SMTP server communication is encrypted with TLS (this can be via `STARTTLS`) or SMTP host is localhost. See [Email Setup]({{< relref "doc/usage/email-setup.en-us.md" >}}) for more information.
+- `ENABLE_HELO`: **true**: Enable HELO operation.
+- `HELO_HOSTNAME`: **(retrieved from system)**: HELO hostname.
+- `FROM`: **\<empty\>**: Mail from address, RFC 5322. This can be just an email address, or the "Name" \<email@example.com\> format.
+- `ENVELOPE_FROM`: **\<empty\>**: Address set as the From address on the SMTP mail envelope. Set to `<>` to send an empty address.
 - `SUBJECT_PREFIX`: **\<empty\>**: Prefix to be placed before e-mail subject lines.
- `MAILER_TYPE`: **smtp**: \[smtp, sendmail, dummy\]
-  - **smtp** Use SMTP to send mail
-  - **sendmail** Use the operating system's `sendmail` command instead of SMTP.
-   This is common on Linux systems.
-  - **dummy** Send email messages to the log as a testing phase.
-  - Note that enabling sendmail will ignore all other `mailer` settings except `ENABLED`,
-     `FROM`, `SUBJECT_PREFIX` and `SENDMAIL_PATH`.
-  - Enabling dummy will ignore all settings except `ENABLED`, `SUBJECT_PREFIX` and `FROM`.
- `SENDMAIL_PATH`: **sendmail**: The location of sendmail on the operating system (can be
-   command or full path).
- `SENDMAIL_ARGS`: **_empty_**: Specify any extra sendmail arguments. (NOTE: you should be aware that email addresses can look like options - if your `sendmail` command takes options you must set the option terminator `--`)
+- `SENDMAIL_PATH`: **sendmail**: The location of sendmail on the operating system (can be command or full path).
+- `SENDMAIL_ARGS`: **\<empty\>**: Specify any extra sendmail arguments. (NOTE: you should be aware that email addresses can look like options - if your `sendmail` command takes options you must set the option terminator `--`)
 - `SENDMAIL_TIMEOUT`: **5m**: default timeout for sending email through sendmail
 - `SENDMAIL_CONVERT_CRLF`: **true**: Most versions of sendmail prefer LF line endings rather than CRLF line endings. Set this to false if your version of sendmail requires CRLF line endings.
 - `SEND_BUFFER_LEN`: **100**: Buffer length of mailing queue. **DEPRECATED** use `LENGTH` in `[queue.mailer]`
+- `SEND_AS_PLAIN_TEXT`: **false**: Send mails only in plain text, without HTML alternative.

 ## Cache (`cache`)

--- a/modules/setting/mailer.go
+++ b/modules/setting/mailer.go
@ -5,7 +5,9 @@
 package setting

 import (
+	"net"
 	"net/mail"
+	"strings"
 	"time"

 	"code.gitea.io/gitea/modules/log"
@ -23,18 +25,19 @@ type Mailer struct {
 	FromName             string
 	FromEmail            string
 	SendAsPlainText      bool
-	MailerType           string
 	SubjectPrefix        string

 	// SMTP sender
-	Host              string
-	User, Passwd      string
-	DisableHelo       bool
-	HeloHostname      string
-	SkipVerify        bool
-	UseCertificate    bool
-	CertFile, KeyFile string
-	IsTLSEnabled      bool
+	Protocol             string
+	SMTPAddr             string
+	SMTPPort             string
+	User, Passwd         string
+	EnableHelo           bool
+	HeloHostname         string
+	ForceTrustServerCert bool
+	UseClientCert        bool
+	ClientCertFile       string
+	ClientKeyFile        string

 	// Sendmail sender
 	SendmailPath        string
@ -56,19 +59,19 @@ func newMailService() {
 	MailService = &Mailer{
 		Name:            sec.Key("NAME").MustString(AppName),
 		SendAsPlainText: sec.Key("SEND_AS_PLAIN_TEXT").MustBool(false),
-		MailerType:      sec.Key("MAILER_TYPE").In("", []string{"smtp", "sendmail", "dummy"}),

-		Host:           sec.Key("HOST").String(),
-		User:           sec.Key("USER").String(),
-		Passwd:         sec.Key("PASSWD").String(),
-		DisableHelo:    sec.Key("DISABLE_HELO").MustBool(),
-		HeloHostname:   sec.Key("HELO_HOSTNAME").String(),
-		SkipVerify:     sec.Key("SKIP_VERIFY").MustBool(),
-		UseCertificate: sec.Key("USE_CERTIFICATE").MustBool(),
-		CertFile:       sec.Key("CERT_FILE").String(),
-		KeyFile:        sec.Key("KEY_FILE").String(),
-		IsTLSEnabled:   sec.Key("IS_TLS_ENABLED").MustBool(),
-		SubjectPrefix:  sec.Key("SUBJECT_PREFIX").MustString(""),
+		Protocol:             sec.Key("PROTOCOL").In("", []string{"smtp", "smtps", "smtp+startls", "smtp+unix", "sendmail", "dummy"}),
+		SMTPAddr:             sec.Key("SMTP_ADDR").String(),
+		SMTPPort:             sec.Key("SMTP_PORT").String(),
+		User:                 sec.Key("USER").String(),
+		Passwd:               sec.Key("PASSWD").String(),
+		EnableHelo:           sec.Key("ENABLE_HELO").MustBool(true),
+		HeloHostname:         sec.Key("HELO_HOSTNAME").String(),
+		ForceTrustServerCert: sec.Key("FORCE_TRUST_SERVER_CERT").MustBool(false),
+		UseClientCert:        sec.Key("USE_CLIENT_CERT").MustBool(false),
+		ClientCertFile:       sec.Key("CLIENT_CERT_FILE").String(),
+		ClientKeyFile:        sec.Key("CLIENT_KEY_FILE").String(),
+		SubjectPrefix:        sec.Key("SUBJECT_PREFIX").MustString(""),

 		SendmailPath:        sec.Key("SENDMAIL_PATH").MustString("sendmail"),
 		SendmailTimeout:     sec.Key("SENDMAIL_TIMEOUT").MustDuration(5 * time.Minute),
@ -77,26 +80,123 @@ func newMailService() {
 	MailService.From = sec.Key("FROM").MustString(MailService.User)
 	MailService.EnvelopeFrom = sec.Key("ENVELOPE_FROM").MustString("")

-	// FIXME: DEPRECATED to be removed in v1.18.0
-	deprecatedSetting("mailer", "ENABLE_HTML_ALTERNATIVE", "mailer", "SEND_AS_PLAIN_TEXT")
-	if sec.HasKey("ENABLE_HTML_ALTERNATIVE") {
-		MailService.SendAsPlainText = !sec.Key("ENABLE_HTML_ALTERNATIVE").MustBool(false)
-	}
-
-	// FIXME: DEPRECATED to be removed in v1.18.0
-	deprecatedSetting("mailer", "USE_SENDMAIL", "mailer", "MAILER_TYPE")
-	if sec.HasKey("USE_SENDMAIL") {
-		if MailService.MailerType == "" && sec.Key("USE_SENDMAIL").MustBool(false) {
-			MailService.MailerType = "sendmail"
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "MAILER_TYPE", "mailer", "PROTOCOL")
+	if sec.HasKey("MAILER_TYPE") && !sec.HasKey("PROTOCOL") {
+		if sec.Key("MAILER_TYPE").String() == "sendmail" {
+			MailService.Protocol = "sendmail"
 		}
 	}

-	parsed, err := mail.ParseAddress(MailService.From)
-	if err != nil {
-		log.Fatal("Invalid mailer.FROM (%s): %v", MailService.From, err)
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "HOST", "mailer", "SMTP_ADDR")
+	if sec.HasKey("HOST") && !sec.HasKey("SMTP_ADDR") {
+		givenHost := sec.Key("HOST").String()
+		addr, port, err := net.SplitHostPort(givenHost)
+		if err != nil {
+			log.Fatal("Invalid mailer.HOST (%s): %v", givenHost, err)
+		}
+		MailService.SMTPAddr = addr
+		MailService.SMTPPort = port
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "IS_TLS_ENABLED", "mailer", "PROTOCOL")
+	if sec.HasKey("IS_TLS_ENABLED") && !sec.HasKey("PROTOCOL") {
+		if sec.Key("IS_TLS_ENABLED").MustBool() {
+			MailService.Protocol = "smtps"
+		} else {
+			MailService.Protocol = "smtp+startls"
+		}
+	}
+
+	if MailService.SMTPPort == "" {
+		switch MailService.Protocol {
+		case "smtp":
+			MailService.SMTPPort = "25"
+		case "smtps":
+			MailService.SMTPPort = "465"
+		case "smtp+startls":
+			MailService.SMTPPort = "587"
+		}
+	}
+
+	if MailService.Protocol == "" {
+		if strings.ContainsAny(MailService.SMTPAddr, "/\\") {
+			MailService.Protocol = "smtp+unix"
+		} else {
+			switch MailService.SMTPPort {
+			case "25":
+				MailService.Protocol = "smtp"
+			case "465":
+				MailService.Protocol = "smtps"
+			case "587":
+				MailService.Protocol = "smtp+startls"
+			default:
+				log.Error("unable to infer unspecified mailer.PROTOCOL from mailer.SMTP_PORT = %q, assume using smtps", MailService.SMTPPort)
+				MailService.Protocol = "smtps"
+			}
+		}
+	}
+
+	// we want to warn if users use SMTP on a non-local IP;
+	// we might as well take the opportunity to check that it has an IP at all
+	ips := tryResolveAddr(MailService.SMTPAddr)
+	if MailService.Protocol == "smtp" {
+		for _, ip := range ips {
+			if !ip.IsLoopback() {
+				log.Warn("connecting over insecure SMTP protocol to non-local address is not recommended")
+				break
+			}
+		}
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "DISABLE_HELO", "mailer", "ENABLE_HELO")
+	if sec.HasKey("DISABLE_HELO") && !sec.HasKey("ENABLE_HELO") {
+		MailService.EnableHelo = !sec.Key("DISABLE_HELO").MustBool()
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "SKIP_VERIFY", "mailer", "FORCE_TRUST_SERVER_CERT")
+	if sec.HasKey("SKIP_VERIFY") && !sec.HasKey("FORCE_TRUST_SERVER_CERT") {
+		MailService.ForceTrustServerCert = sec.Key("SKIP_VERIFY").MustBool()
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "USE_CERTIFICATE", "mailer", "USE_CLIENT_CERT")
+	if sec.HasKey("USE_CERTIFICATE") && !sec.HasKey("USE_CLIENT_CERT") {
+		MailService.UseClientCert = sec.Key("USE_CLIENT_CERT").MustBool()
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "CERT_FILE", "mailer", "CLIENT_CERT_FILE")
+	if sec.HasKey("CERT_FILE") && !sec.HasKey("CLIENT_CERT_FILE") {
+		MailService.ClientCertFile = sec.Key("CERT_FILE").String()
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "KEY_FILE", "mailer", "CLIENT_KEY_FILE")
+	if sec.HasKey("KEY_FILE") && !sec.HasKey("CLIENT_KEY_FILE") {
+		MailService.ClientKeyFile = sec.Key("KEY_FILE").String()
+	}
+
+	// FIXME: DEPRECATED to be removed in v1.19.0
+	deprecatedSetting("mailer", "ENABLE_HTML_ALTERNATIVE", "mailer", "SEND_AS_PLAIN_TEXT")
+	if sec.HasKey("ENABLE_HTML_ALTERNATIVE") && !sec.HasKey("SEND_AS_PLAIN_TEXT") {
+		MailService.SendAsPlainText = !sec.Key("ENABLE_HTML_ALTERNATIVE").MustBool(false)
+	}
+
+	if MailService.From != "" {
+		parsed, err := mail.ParseAddress(MailService.From)
+		if err != nil {
+			log.Fatal("Invalid mailer.FROM (%s): %v", MailService.From, err)
+		}
+		MailService.FromName = parsed.Name
+		MailService.FromEmail = parsed.Address
+	} else {
+		log.Error("no mailer.FROM provided, email system may not work.")
 	}
-	MailService.FromName = parsed.Name
-	MailService.FromEmail = parsed.Address

 	switch MailService.EnvelopeFrom {
 	case "":
@ -105,7 +205,7 @@ func newMailService() {
 		MailService.EnvelopeFrom = ""
 		MailService.OverrideEnvelopeFrom = true
 	default:
-		parsed, err = mail.ParseAddress(MailService.EnvelopeFrom)
+		parsed, err := mail.ParseAddress(MailService.EnvelopeFrom)
 		if err != nil {
 			log.Fatal("Invalid mailer.ENVELOPE_FROM (%s): %v", MailService.EnvelopeFrom, err)
 		}
@ -113,11 +213,8 @@ func newMailService() {
 		MailService.EnvelopeFrom = parsed.Address
 	}

-	if MailService.MailerType == "" {
-		MailService.MailerType = "smtp"
-	}
-
-	if MailService.MailerType == "sendmail" {
+	if MailService.Protocol == "sendmail" {
+		var err error
 		MailService.SendmailArgs, err = shellquote.Split(sec.Key("SENDMAIL_ARGS").String())
 		if err != nil {
 			log.Error("Failed to parse Sendmail args: %s with error %v", CustomConf, err)
@ -148,3 +245,21 @@ func newNotifyMailService() {
 	Service.EnableNotifyMail = true
 	log.Info("Notify Mail Service Enabled")
 }
+
+func tryResolveAddr(addr string) []net.IP {
+	if strings.HasPrefix(addr, "[") && strings.HasSuffix(addr, "]") {
+		addr = addr[1 : len(addr)-1]
+	}
+	ip := net.ParseIP(addr)
+	if ip != nil {
+		ips := make([]net.IP, 1)
+		ips[0] = ip
+		return ips
+	}
+	ips, err := net.LookupIP(addr)
+	if err != nil {
+		log.Warn("could not look up mailer.SMTP_ADDR: %v", err)
+		return make([]net.IP, 0)
+	}
+	return ips
+}
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@ -179,7 +179,8 @@ log_root_path_helper = Log files will be written to this directory.

 optional_title = Optional Settings
 email_title = Email Settings
-smtp_host = SMTP Host
+smtp_addr = SMTP Host
+smtp_port = SMTP Port
 smtp_from = Send Email As
 smtp_from_helper = Email address Gitea will use. Enter a plain email address or use the "Name" <email@example.com> format.
 mailer_user = SMTP Username
--- a/routers/install/install.go
+++ b/routers/install/install.go
@ -133,7 +133,8 @@ func Install(ctx *context.Context) {

 	// E-mail service settings
 	if setting.MailService != nil {
-		form.SMTPHost = setting.MailService.Host
+		form.SMTPAddr = setting.MailService.SMTPAddr
+		form.SMTPPort = setting.MailService.SMTPPort
 		form.SMTPFrom = setting.MailService.From
 		form.SMTPUser = setting.MailService.User
 		form.SMTPPasswd = setting.MailService.Passwd
@ -421,9 +422,10 @@ func SubmitInstall(ctx *context.Context) {
 		cfg.Section("server").Key("LFS_START_SERVER").SetValue("false")
 	}

-	if len(strings.TrimSpace(form.SMTPHost)) > 0 {
+	if len(strings.TrimSpace(form.SMTPAddr)) > 0 {
 		cfg.Section("mailer").Key("ENABLED").SetValue("true")
-		cfg.Section("mailer").Key("HOST").SetValue(form.SMTPHost)
+		cfg.Section("mailer").Key("SMTP_ADDR").SetValue(form.SMTPAddr)
+		cfg.Section("mailer").Key("SMTP_PORT").SetValue(form.SMTPPort)
 		cfg.Section("mailer").Key("FROM").SetValue(form.SMTPFrom)
 		cfg.Section("mailer").Key("USER").SetValue(form.SMTPUser)
 		cfg.Section("mailer").Key("PASSWD").SetValue(form.SMTPPasswd)
--- a/routers/web/admin/auths.go
+++ b/routers/web/admin/auths.go
@ -159,7 +159,7 @@ func parseLDAPConfig(form forms.AuthenticationForm) *ldap.Source {
 func parseSMTPConfig(form forms.AuthenticationForm) *smtp.Source {
 	return &smtp.Source{
 		Auth:           form.SMTPAuth,
-		Host:           form.SMTPHost,
+		Addr:           form.SMTPAddr,
 		Port:           form.SMTPPort,
 		AllowedDomains: form.AllowedDomains,
 		ForceSMTPS:     form.ForceSMTPS,
--- a/services/auth/source/smtp/auth.go
+++ b/services/auth/source/smtp/auth.go
@ -58,10 +58,10 @@ var ErrUnsupportedLoginType = errors.New("Login source is unknown")
 func Authenticate(a smtp.Auth, source *Source) error {
 	tlsConfig := &tls.Config{
 		InsecureSkipVerify: source.SkipVerify,
-		ServerName:         source.Host,
+		ServerName:         source.Addr,
 	}

-	conn, err := net.Dial("tcp", net.JoinHostPort(source.Host, strconv.Itoa(source.Port)))
+	conn, err := net.Dial("tcp", net.JoinHostPort(source.Addr, strconv.Itoa(source.Port)))
 	if err != nil {
 		return err
 	}
@ -71,7 +71,7 @@ func Authenticate(a smtp.Auth, source *Source) error {
 		conn = tls.Client(conn, tlsConfig)
 	}

-	client, err := smtp.NewClient(conn, source.Host)
+	client, err := smtp.NewClient(conn, source.Addr)
 	if err != nil {
 		return fmt.Errorf("failed to create NewClient: %w", err)
 	}
--- a/services/auth/source/smtp/source.go
+++ b/services/auth/source/smtp/source.go
@ -19,7 +19,7 @@ import (
 // Source holds configuration for the SMTP login source.
 type Source struct {
 	Auth           string
-	Host           string
+	Addr           string
 	Port           int
 	AllowedDomains string `xorm:"TEXT"`
 	ForceSMTPS     bool
--- a/services/auth/source/smtp/source_authenticate.go
+++ b/services/auth/source/smtp/source_authenticate.go
@ -32,7 +32,7 @@ func (source *Source) Authenticate(user *user_model.User, userName, password str
 	var auth smtp.Auth
 	switch source.Auth {
 	case PlainAuthentication:
-		auth = smtp.PlainAuth("", userName, password, source.Host)
+		auth = smtp.PlainAuth("", userName, password, source.Addr)
 	case LoginAuthentication:
 		auth = &loginAuthenticator{userName, password}
 	case CRAMMD5Authentication:
--- a/services/forms/auth_form.go
+++ b/services/forms/auth_form.go
@ -45,7 +45,7 @@ type AuthenticationForm struct {
 	IsActive                      bool
 	IsSyncEnabled                 bool
 	SMTPAuth                      string
-	SMTPHost                      string
+	SMTPAddr                      string
 	SMTPPort                      int
 	AllowedDomains                string
 	SecurityProtocol              int `binding:"Range(0,2)"`
--- a/services/forms/user_form.go
+++ b/services/forms/user_form.go
@ -40,7 +40,8 @@ type InstallForm struct {
 	AppURL       string `binding:"Required"`
 	LogRootPath  string `binding:"Required"`

-	SMTPHost        string
+	SMTPAddr        string
+	SMTPPort        string
 	SMTPFrom        string
 	SMTPUser        string `binding:"OmitEmpty;MaxSize(254)" locale:"install.mailer_user"`
 	SMTPPasswd      string
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@ -147,65 +147,82 @@ type smtpSender struct{}
 func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 	opts := setting.MailService

-	host, port, err := net.SplitHostPort(opts.Host)
+	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 err
-	}
-
-	tlsconfig := &tls.Config{
-		InsecureSkipVerify: opts.SkipVerify,
-		ServerName:         host,
-	}
-
-	if opts.UseCertificate {
-		cert, err := tls.LoadX509KeyPair(opts.CertFile, opts.KeyFile)
-		if err != nil {
-			return err
-		}
-		tlsconfig.Certificates = []tls.Certificate{cert}
-	}
-
-	conn, err := net.Dial("tcp", net.JoinHostPort(host, port))
-	if err != nil {
-		return err
+		return fmt.Errorf("failed to establish network connection to SMTP server: %v", err)
 	}
 	defer conn.Close()

-	isSecureConn := opts.IsTLSEnabled || (strings.HasSuffix(port, "465"))
-	// Start TLS directly if the port ends with 465 (SMTPS protocol)
-	if isSecureConn {
+	var tlsconfig *tls.Config
+	if opts.Protocol == "smtps" || opts.Protocol == "smtp+startls" {
+		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: %v", 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("NewClient: %v", err)
+		return fmt.Errorf("could not initiate SMTP session: %v", err)
 	}

-	if !opts.DisableHelo {
+	if opts.EnableHelo {
 		hostname := opts.HeloHostname
 		if len(hostname) == 0 {
 			hostname, err = os.Hostname()
 			if err != nil {
-				return err
+				return fmt.Errorf("could not retrieve system hostname: %v", err)
 			}
 		}

 		if err = client.Hello(hostname); err != nil {
-			return fmt.Errorf("Hello: %v", err)
+			return fmt.Errorf("failed to issue HELO command: %v", err)
 		}
 	}

-	// If not using SMTPS, always use STARTTLS if available
-	hasStartTLS, _ := client.Extension("STARTTLS")
-	if !isSecureConn && hasStartTLS {
-		if err = client.StartTLS(tlsconfig); err != nil {
-			return fmt.Errorf("StartTLS: %v", err)
+	if opts.Protocol == "smtp+startls" {
+		hasStartTLS, _ := client.Extension("STARTTLS")
+		if hasStartTLS {
+			if err = client.StartTLS(tlsconfig); err != nil {
+				return fmt.Errorf("failed to start TLS connection: %v", err)
+			}
+		} else {
+			log.Warn("StartTLS requested, but SMTP server does not support it; falling back to regular SMTP")
 		}
 	}

 	canAuth, options := client.Extension("AUTH")
-	if canAuth && len(opts.User) > 0 {
+	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") {
@ -219,34 +236,34 @@ func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {

 		if auth != nil {
 			if err = client.Auth(auth); err != nil {
-				return fmt.Errorf("Auth: %v", err)
+				return fmt.Errorf("failed to authenticate SMTP: %v", err)
 			}
 		}
 	}

 	if opts.OverrideEnvelopeFrom {
 		if err = client.Mail(opts.EnvelopeFrom); err != nil {
-			return fmt.Errorf("Mail: %v", err)
+			return fmt.Errorf("failed to issue MAIL command: %v", err)
 		}
 	} else {
 		if err = client.Mail(from); err != nil {
-			return fmt.Errorf("Mail: %v", err)
+			return fmt.Errorf("failed to issue MAIL command: %v", err)
 		}
 	}

 	for _, rec := range to {
 		if err = client.Rcpt(rec); err != nil {
-			return fmt.Errorf("Rcpt: %v", err)
+			return fmt.Errorf("failed to issue RCPT command: %v", err)
 		}
 	}

 	w, err := client.Data()
 	if err != nil {
-		return fmt.Errorf("Data: %v", err)
+		return fmt.Errorf("failed to issue DATA command: %v", err)
 	} else if _, err = msg.WriteTo(w); err != nil {
-		return fmt.Errorf("WriteTo: %v", err)
+		return fmt.Errorf("SMTP write failed: %v", err)
 	} else if err = w.Close(); err != nil {
-		return fmt.Errorf("Close: %v", err)
+		return fmt.Errorf("SMTP close failed: %v", err)
 	}

 	return client.Quit()
@ -338,13 +355,13 @@ func NewContext() {
 		return
 	}

-	switch setting.MailService.MailerType {
-	case "smtp":
-		Sender = &smtpSender{}
+	switch setting.MailService.Protocol {
 	case "sendmail":
 		Sender = &sendmailSender{}
 	case "dummy":
 		Sender = &dummySender{}
+	default:
+		Sender = &smtpSender{}
 	}

 	mailQueue = queue.CreateQueue("mail", func(data ...queue.Data) []queue.Data {
--- a/templates/install.tmpl
+++ b/templates/install.tmpl
@ -173,8 +173,12 @@
 							{{.locale.Tr "install.email_title"}}
 						</summary>
 						<div class="inline field">
-							<label for="smtp_host">{{.locale.Tr "install.smtp_host"}}</label>
-							<input id="smtp_host" name="smtp_host" value="{{.smtp_host}}">
+							<label for="smtp_addr">{{.locale.Tr "install.smtp_addr"}}</label>
+							<input id="smtp_addr" name="smtp_addr" value="{{.smtp_addr}}">
+						</div>
+						<div class="inline field">
+							<label for="smtp_port">{{.locale.Tr "install.smtp_port"}}</label>
+							<input id="smtp_port" name="smtp_port" value="{{.smtp_port}}">
 						</div>
 						<div class="inline field {{if .Err_SMTPFrom}}error{{end}}">
 							<label for="smtp_from">{{.locale.Tr "install.smtp_from"}}</label>