audriga GmbH This document describes a machine-readable format for conveying unavailibility information in email messages. This includes "vacation notices" of persons but also different forms of unavailibility for emails sent by programs. Structured vacation notices are supposed to be used in conjunction with conventional, human-readable vacation notices in most cases. They are based on the forthcoming "structured email" specification defined in [I-D.ietf-sml-structured-email-03] and related drafts.