macbook mail attachment file could not be opened because it is empty

attachments show the "downloading" icon, but it doesn't download anything. save attachment to desktop and try to open it and i get "The file “20150912.jpg” could not be opened because it is empty". happens with all types of attachments. if i right click on the attachment, the submenu only has two options: copy and speech. and can't "quick look" attachment. not sure how to solve this problem. hope someone could point me in the solution direction.