How to send a notice politely in a group?

Include greeting, subject, text and ending.

1. Greetings: The notice should start with a polite greeting, such as "Hello everyone" and "Dear friend".

2. Theme: The theme of the notice should be concise and clear, so that people can see it at a glance.

3. Text: The text of the notice should include the background and reason of the activity, the time and place of the activity, the content and requirements of the activity.

4. Ending: The notice should end in a polite way.