For your guest, any kind of messages may be sent to them which are very important for your guest. If any known person of your guest wants to register his/her message, you should have to go with this path; Utility>Guest message.
A following window will appear to you as;
Then you will see a window regarding this on which at the top of right corner you get a option of New Message with plus mark. When you click on this option for writing New Message a simple window will exist there where you will select name of your guest, Message Book, and write message for the guest;
Once you fill up above message box you need to save for delivering it to your guest . After that your saved message automatically will be updated in the following window, which will tell you to deliver guest’s message. You will deliver this message by pressing Deliver key. In case if you miss to deliver guest message, you can check it by clicking on Show Undelivered Message Only. The window will exist there as;