There's a merged pull request on the mblaze repository

improve named part/attachment detection
https://github.com/leahneukirchen/mblaze/pull/232

Description:
This will add filename detection for parts which specify Content-Disposition _without_ a filename parameter and Content-Type _with_ a name parameter. I'm not sure whether omitting this possibility was intentional, e.g. to adhere to standard, but messages which name their attachments in this way occur in the wild.