Apple Mail not downloading attachments I am using macOS Sierra. Recently, the Mail app started having problems with attachments. On many (but not all) messages, attachments show up, but they are displayed as "Mail Attachment", not as the actual file name. Curiously, sometimes the correct icon shows up. I thought that maybe they needed some time to download, but waiting for hours does not solve it. I tried turning on and off the automatic attachment download and deleting the Mail Downloads directory, but that did not fix it.

This is an Exchange account, which may be part of the problem.

Any idea what could be causing this?
I found this post to be very interesting: 

http://osxdaily.com/2016/12/17/fix-mail-not-showing-attachments-mac/


Backup your computer 
Rebuild your email mailbox(es) (this may take a long time to run, be sure your connected to internet because it's going to reload all the mails) 
In your "Account Information", select Download Attachement that matters to you (all)
Restart Mail.


Hope that helps