I made this to crawl all the PDF files from my IMAP inbox. You can write custom "validators" if you are not looking for PDFs.
get_files_from_imap.py -h has (almost) all the info you will need
get_files_from_imap.py cfg will download files based on config.ini
look at get_files_from_imap.py cfg -h for more info
get_files_from_imap.py cli <hostname> <username> <password> will download all attachments ending in ".pdf" to /tmp
look at get_files_from_imap.py cli -h for more info