Files with .dmmx extension are old mind map bundles from DropMind (iMindQ) software. Use DropMind or iMindQ to open them. Can possibly export them to other map formats. The DMMX files contain a compressed XML file named document.xml and a preview.png image file showing the mind map.
DMMX is a file extension for DropMind XML map bundles, created by Seavus. Compatible with iOS, Linux, Mac OS, Windows. DMMX file format belongs to Data Files category like 1326 other extensions. DropMind supports DMMX files, yet 3 other tools may also open them.
When Windows doesn’t recognize the DMMX extension, it asks to select an app to open the file. Update the application you normally use to open DMMX files, as only the latest version supports the current format. You can scan the DMMX file with antivirus software like Norton or Nod32 to check for viruses.
Here are tips on how to open DMMX files and programs that support them. The second way is to associate the DMMX extension with the software in Windows Registry. Many files contain only simple text data.