Adds an attachment to an item. Using X00 will work for the messageID if the item view is showing.
AFTKN_ITEM_ATTACHMENT_ADD or 665
VOID ItemAttachmentAdd(ANSISTRING MessageID; ENUM AttachmentClass; ANSISTRING AttachmentName; [ANSISTRING AttachmentDisplayname])
Unique item identifier, returned by ItemMessageIDFromView().
Type of attachment:
Name of an attachment.
(Optional) Name displayed in the Attach File box.