| .CAL | Newera Software Technology, Inc. | Rasterbilledfiler | CALS Raster File | Microsoft Outlook | Microsoft Corporation |
| .CLX | IBM | Datafiler | Rational XDE | Microsoft Outlook | Microsoft Corporation |
| .CVR | Microsoft Corporation | Ikke Almindelige Filer | Microsoft Crash Report File | Microsoft Outlook | Microsoft Corporation |
| .DICPROOF | Microsoft Corporation | Indstillingsfiler | Microsoft Dictionary Proofing File | Microsoft Outlook | Microsoft Corporation |
| .DISPOSITION-NOTIFICATION | Microsoft Corporation | Webfiler | Message Disposition Notification | Microsoft Outlook | Microsoft Corporation |
| .ECF | Microsoft Corporation | Plug-in-filer | Outlook Add-in | Microsoft Outlook | Microsoft Corporation |
| .FAV | Microsoft Corporation | Indstillingsfiler | Microsoft Outlook Bar-Shortcut | Microsoft Outlook | Microsoft Corporation |
| .FFA | Microsoft Corporation | Systemfiler | Find Fast Status File | Microsoft Outlook | Microsoft Corporation |
| .FFO | Microsoft Corporation | Systemfiler | Find Fast Document Properties Cache | Microsoft Outlook | Microsoft Corporation |
| .FFT | Adobe Systems Incorporated | Plug-in-filer | Adobe Audition Noise Print File | Microsoft Outlook | Microsoft Corporation |
| .FFX | Adobe Systems Incorporated | Indstillingsfiler | After Effects Preset File | Microsoft Outlook | Microsoft Corporation |
| .ICAL | Open Source | Ikke Almindelige Filer | iCalendar File | Microsoft Outlook | Microsoft Corporation |
| .ICALENDAR | Open Source | Ikke Almindelige Filer | iCalendar File | Microsoft Outlook | Microsoft Corporation |
| .ICS | IronCAD, LLC | CAD-filer | IronCAD 3D CAD Drawing File | Microsoft Outlook | Microsoft Corporation |
| .MIME | Various Developers | Kodet filer | Multi-Purpose Internet Mail Extension | Microsoft Outlook | Microsoft Corporation |
| .MME | Smith Micro Software | Kodet filer | Multipurpose Internet Mail Extensions | Microsoft Outlook | Microsoft Corporation |
| .MMF | Microsoft Corporation | Datafiler | Microsoft Message File | Microsoft Outlook | Microsoft Corporation |
| .MSG | Microsoft Corporation | Tekstfiler | Saved Email Message | Microsoft Outlook | Microsoft Corporation |
| .MSO | Microsoft Corporation | Datafiler | Microsoft Organization Chart Data File | Microsoft Outlook | Microsoft Corporation |
| .NICK | Microsoft Corporation | Ikke Almindelige Filer | Microsoft Outlook Nickname File | Microsoft Outlook | Microsoft Corporation |
| .NK2 | Microsoft Corporation | Ikke Almindelige Filer | Outlook 2002 Nickname File | Microsoft Outlook | Microsoft Corporation |
| .NST | Microsoft Corporation | Datafiler | Outlook Connector For Notes File | Microsoft Outlook | Microsoft Corporation |
| .OAB | Microsoft Corporation | Datafiler | Offline Address Book | Microsoft Outlook | Microsoft Corporation |
| .OFT | Microsoft Corporation | Datafiler | Outlook File Template | Microsoft Outlook | Microsoft Corporation |
| .OSS | Microsoft Corporation | Indstillingsfiler | Microsoft Outlook Saved Search File | Microsoft Outlook | Microsoft Corporation |
| .P10 | Open Source | Ikke Almindelige Filer | Certificate Request File | Microsoft Outlook | Microsoft Corporation |
| .PAB | Microsoft Corporation | Datafiler | Personal Address Book | Microsoft Outlook | Microsoft Corporation |
| .PSW | Microsoft Corporation | Ikke Almindelige Filer | Windows Password Reset Disk File | Microsoft Outlook | Microsoft Corporation |
| .PWI | Microsoft Corporation | Tekstfiler | Pocket Word Document | Microsoft Outlook | Microsoft Corporation |
| .SAGE | Sage | Krypterede Filer | Sage Ransomware Affected Data | Microsoft Outlook | Microsoft Corporation |
| .SIG | Unknown Developer | Tekstfiler | Signature File | Microsoft Outlook | Microsoft Corporation |
| .SRS | Microsoft Corporation | Indstillingsfiler | Outlook Send/Receive Settings File | Microsoft Outlook | Microsoft Corporation |
| .TNEF | Microsoft Corporation | Ikke Almindelige Filer | Transport Neutral Encapsulation Format | Microsoft Outlook | Microsoft Corporation |
| .VCS | Microsoft Corporation | Datafiler | vCalendar Event File | Microsoft Outlook | Microsoft Corporation |
| .WAB | Microsoft Corporation | Datafiler | Windows Address Book | Microsoft Outlook | Microsoft Corporation |
| .XNK | Microsoft Corporation | Ikke Almindelige Filer | Microsoft Exchange Public Folder Shortcut | Microsoft Outlook | Microsoft Corporation |
| .ZDB | Synacor Inc. | Datafiler | Zimbra Database File | Microsoft Outlook | Microsoft Corporation |
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