System alerts are automatically deleted in Raven after 6 months. These are alerts you set in Preferences > Change Notifications for things like link changes. System messages between users and other messages such as Basecamp tasks do not have an expiration date.
Create a New System Message
Select New Message from the Message Icon.
Or additionally create a Contextual Message by clicking the Contextual Message option. Contextual messages include the URL of the item you're viewing for the recipient's reference.
Create a Message. Add the recipient (a Raven subuser with access to Messages), a subject and message.
Click the Send button.
Edit a System Message
Click a message subject to view the message. From here you can delete the message or add a reply. If a new participant is added they will be shared the thread and see future replies.
In Message you can view All, Messages, Alerts, Sent and Trash. Messages are notes sent from Raven users.
Alerts are Raven alerts each user can turn on or off in Preferences > Change Notifications. Basecamp Messages do not trigger Raven alerts. System Alerts are automatically deleted after 6 months.
Additionally you can select multiple messages using the checkboxes and use the Bulk Actions menu to mark messages as read or unread as well as delete messages in bulk.
Filter are used to refine the list of messages you want to view. You can filter by Include or Exclude options. To create a new filter, click on filter icon and click on Create New Filter.