| mlib | SAM Model Library Data |
| mlis | Stog MLIS Data |
| mllr | CMU Sphinx MLLR Data |
| mlml | Multi-line Markup Language Document |
| mln | Alchemy Markov Logic Network Data |
| mln | Mauve Alignment Data |
| mlog | Microsoft Outlook Message Log |
| mlp | mAirList Desktop Playlist |
| mlp | Martus Language Pack |
| mls | mAirList Script |
| mlsxml | Skype XML Data |
| mlt | mAirList Desktop Template |
| mlw | MainLog Data |
| mlx | Meshlab Filter Script |
| mlz | MLZ Data |
| mm | FreeMind MindMap |
| mm | Matrix Market File |
| mm3 | Mortgage Minder v3 Data File |
| mm3d | Misfit Model 3D Model |
| mm6 | Money Manager 6 Data |
| mmads | MMADS Chemical Modeller Input Data |
| mmap | MindManager Map File |
| mmas | MindManager Theme |
| mmat | MindManager Map Template |
| mmb | Mobile Master Backup |
| mmc | Microsoft ClipArt Gallery Catalog |
| mmcif | mmCIF Data |
| mmcollection | Mail Manager Collection Data |
| mmd | mAirList Metadata |
| mmd | Media Processing Server Audio Data |
| mmd0 | Foobar2000 Data |
| mmdb | MaxMind GeoIP2 Database |
| mmdb | Molecular Modeling Database |
| mmdl | Sapphire Structure Model Data |
| mme | MIME Encoded Data |