1. A method, comprising: identifying metadata associated with a new message by one or more computing devices, the new message being associated with a conversation thread; adding the metadata by the one or more computing devices to conversation metadata associated with the conversation thread and attached to a first anchor message associated with the conversation thread to create aggregate thread data as an extension to a header of the first anchor message; and moving the aggregate thread data by the one or more computing devices from the first anchor message to the new message to form a next anchor message as an extension to a header of the new message such that the metadata associated with the conversation thread is no longer attached to the first anchor message.