Attachments can be added to tasks when issuing a storetodos command. Use the sendattach parameter to specify whether an actual attachment is being sent as part of the iTIP data, "0" for none, and "1" for attachment present in data.
In addition, you can delete existing attachments from a task using the deleteattach parameter. The task is not deleted. The deleteattach values are the attachment ID's emitted in the X-S1CS-ATTACH-ID X-Token as part of the VEVENT returned for a fetch command.
In earlier versions of Calendar Server, attachments could only be sent as a reference (URL) to a Web location. The attachments parameter was used to hold the URL.
The attachments parameter has been deprecated. It remains functional in this release only for backward compatibility. Change any scripts you have that use the old parameter to the new attachment model.