| mbox | Unix Mailbox |
| mbp | Mobipocket Reader Data |
| mbp | Modbus Poll Data File |
| mbp | MyBackup Pro Database |
| mbs | Micrografx Picture Publisher Brush Shape |
| mbs | Opera Mail Mailbox |
| mbsa | Microsoft Baseline Security Analyser Report |
| mbsb | Mamut Enterprise Database Backup |
| mbsyncstate | mbsync Folder Backup |
| mbt | ecBuilder Template |
| mbtemplate | ModelBaker Custom Template Data |
| mbtemplate | Modelbench Scene Template |
| mbu | Sony CAV-M1000ES Memory Backup |
| mbv | Everio MediaBrowser Edit Data |
| mbw | Easy Mail Backup Wizard Data |
| mbw | MBRWizard MBR Backup |
| mbx | Eudora Mailbox File |
| mbx | Microsoft Outlook Express v4 Mailbox |
| mc | MetaCard Stack Data |
| mc1 | MedCalc Data |
| mc3 | MC3D Document |
| mc4 | MicroCase v4 Data File |
| mc4d | Maxon Cinema 4D Object |
| mc5 | Poser 5 Material Collection |
| mc6 | Poser 6 Material Collection |
| mcacc | MCACC Measurement Data |
| mcapm | PocketMine-MP Minecraft Anvil Data |
| mcat | Meerecat File Guard Encrypted Data |
| mcb | NEPLAN Root Network Data |
| mcc | Amiga MUI External Class Data |
| mcc | Mathcad Configuration Data |
| mcd | Bleem! Memory Card Save Data |
| mcd | MiniCAD Design Data |
| mcdata | MCData XML Data |
| mcdb | Media Cache Database |
