Have you ever heard about CuckooMX? It is a project by Xavier Mertens, you can read it at http://blog.rootshell.be/2012/06/20/cuckoomx-automating-email-attachments-scanning-with-cuckoo/.
CuckooMX automatically sends all the e-mail attachments to Cuckoo Sandbox, obviously, so that it can be analyzed whether the attachments—of types such as PDF, MS Office, ZIP, or other executable files—contain malware or not.
Here is a figure that might help us get a better picture of what CuckooMX does:
In the preceding figure, we can see that CuckooMX performs these tasks: