TwitHaven is designed as an internal messaging system useful for sending short messages and attachments without the complexities of email and SMS text systems.
Messages can be sent to an individual or a group of users (you must be a member of that group to send to it) or both. All messages have a start and expiry date and time. This allows you to create a series of messages at the start of the year to remind users of upcoming events yet the message will not appear on their computers until the time has come. Also messages will expire so there is no need to remind people of events after the event is over.
TwitHaven is available for any of Macintosh, Windows and Linux, it is available on the Cloud so there is no longer any excuse for people being uninformed. The sender can always check to see who has accepted the Message or not.