Thank you for your (recent) e-mail. We are sorry for the delay in replying to you, but We are pleased to inform you that we are in progress reviewing the matter and we'll inform you the result soon
I suggest you delete the "We are pleased to inform you" part. First YIU delay in responding at all and then you say it's still not resolved. If I were your customer I would not find that pleasing information.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.