At my company our enterprise content management system recognizes Mindmanager mmap files similarly to MS Office files, ie you can upload, they keep the extension, if you have the Mindmanager application and edit a file, it opens in the app, etc. Efficient.
In our Jive 7 community, I find that the system does not recognize a mmap file I upload and attaches a zip extension, presumably what it does when an unrecognized file type is uploaded.
Any possibility you could support mmap files at least to the extent of recognizing them so that sharing via Jive could be a more seamless and not a two-step process for people accessing the file? (download, unzip)