You may also say what the attachments include. You always have to let your reader know what to look for when you are sending a memo. Readers cannot guess what the contents might be. Why The first sentence of your memo remains paramount. You have to remind the reader that you have a purpose for writing.
People have to know why they have to read communications.
You don't keep the news from them by waiting until the end of the first paragraph. You can then go into the details of who, what, where, and when as you develop the first paragraph. Memos demand purposes. Too much paper and electronic communication exist for people to waste their time on thoughtless memos ill prepared and ill conceived. Next, look at the length of your paragraphs.