[bugfix/email] Don't use plainAuth when no smtp username/password provided (#3332)

* Do not use plainAuth when no user or password. Fixes #3320

* formatting

---------

Co-authored-by: Yonas Yanfa <yonas.y@gmail.com>

internal/email/sender.go

@@ -71,17 +71,26 @@ func NewSender() (Sender, error) {
 		return nil, err
 	}
 
-	username := config.GetSMTPUsername()
+	var (
-	password := config.GetSMTPPassword()
+		username  = config.GetSMTPUsername()
-	host := config.GetSMTPHost()
+		password  = config.GetSMTPPassword()
-	port := config.GetSMTPPort()
+		host      = config.GetSMTPHost()
-	from := config.GetSMTPFrom()
+		port      = config.GetSMTPPort()
-	msgIDHost := config.GetHost()
+		from      = config.GetSMTPFrom()
+		msgIDHost = config.GetHost()
+		smtpAuth  smtp.Auth
+	)
+
+	if username == "" || password == "" {
+		smtpAuth = nil
+	} else {
+		smtpAuth = smtp.PlainAuth("", username, password, host)
+	}
 
 	return &sender{
 		hostAddress: fmt.Sprintf("%s:%d", host, port),
 		from:        from,
-		auth:        smtp.PlainAuth("", username, password, host),
+		auth:        smtpAuth,
 		msgIDHost:   msgIDHost,
 		template:    t,
 	}, nil