Translation:I still have not replied to your email. Sorry!
"Reply" is intransitive in this sense, taking an indirect object. You have to reply to a message, in English.
You can also use "reply" like "say", for quoting direct speech, in which case you can say something like "He replied 'no'", but I would say it's more often used with "that", for so-called reported speech: "he replied that he wasn't interested".