fix restore users with MFA config

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

internal/smtp/smtp.go

@@ -181,6 +181,7 @@ func SendEmail(to []string, subject, body string, contentType EmailContentType,
 	}
 
 	email := mail.NewMSG()
+	email.AllowDuplicateAddress = true
 	if from != "" {
 		email.SetFrom(from)
 	} else {