Explicitly decide whether to use TLS in mailer's configuration (#5024)

* explicitly decide on using TLS for mail connections

* explicitly decide on using TLS for mail connections

* keep compatibility

custom/conf/app.ini.sample

@@ -388,6 +388,8 @@ SKIP_VERIFY =
 USE_CERTIFICATE = false
 CERT_FILE = custom/mailer/cert.pem
 KEY_FILE = custom/mailer/key.pem
+; Should SMTP connection use TLS
+IS_TLS_ENABLED = false
 ; Mail from address, RFC 5322. This can be just an email address, or the `"Name" <email@example.com>` format
 FROM =
 ; Mailer user name and password

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -222,6 +222,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
      `FROM` and `SENDMAIL_PATH`.
 - `SENDMAIL_PATH`: **sendmail**: The location of sendmail on the operating system (can be
    command or full path).
+- ``IS_TLS_ENABLED`` :  **false** : Decide if SMTP connections should use TLS.
 
 ## Cache (`cache`)
 

modules/mailer/mailer.go

@@ -122,11 +122,10 @@ func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 	}
 	defer conn.Close()
 
-	isSecureConn := false
+	isSecureConn := opts.IsTLSEnabled || (strings.HasSuffix(port, "465"))
 	// Start TLS directly if the port ends with 465 (SMTPS protocol)
-	if strings.HasSuffix(port, "465") {
+	if isSecureConn {
 		conn = tls.Client(conn, tlsconfig)
-		isSecureConn = true
 	}
 
 	client, err := smtp.NewClient(conn, host)

modules/setting/setting.go

@@ -1523,6 +1523,7 @@ type Mailer struct {
 	SkipVerify        bool
 	UseCertificate    bool
 	CertFile, KeyFile string
+	IsTLSEnabled      bool
 
 	// Sendmail sender
 	UseSendmail  bool
@@ -1556,6 +1557,7 @@ func newMailService() {
 		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(),
 
 		UseSendmail:  sec.Key("USE_SENDMAIL").MustBool(),
 		SendmailPath: sec.Key("SENDMAIL_PATH").MustString("sendmail"),