After viewing an old thread it seems this is much needed. Emails often contain valuable information and attachments that would be worth connecting to an existing task, espeically since not every organizations employees will be users of Asana. Example: requested official approval for use of a third party image and original image for a design project. Received approval - rather than take screen shots of the communication and save the image - imagine how fast it would be to link the email thread to the task as a comment or subtask.
With so many upvotes on the other thread I find it hard to believe this hasn’t been considered.