Here is the steps to reproduce the issue:

1. Install a new JIRA instance and create new project.
2. Set up the mail handler to pick up the local file.
3. Add the file test.eml in the folder <JIRA home directory>/import/mail.
4. Wait for 1 minute to let the handler to read the file to create a new issue:
   
   It seems that the attachment file is not picked up by JIRA.

PS: The file test.eml can be correctly open via Outlook and it shows that there is an attachment file inside.