As comitted to in our post of November 27th, the following is a list of common file extensions used in commericail email. The blog of the 11/27/2012 mentions that an email receipent should never open an attachment from unknown sources. This is doubaly true when a file format is not recognized. If the sender is known and the attachment format is not known or cannot be opened, then the sender should be notified and an adjustment made to accomodate having the intended content delivered via different means. Commonly this would be sending the file in a format the sendee can read.

List of File Extensions

        File extensions are based on utilizing possible combinations of English characters.  Three alpha characters allow for a combination of close to 20,000 possibilities.  If numbers or additional letters are added, far more combinations are possible.  There are a number of categories for file extensions.  Among these are compression data archive, media archiving, computer aided design, database, fonts, graphs (vector, 3D), object code, source code and music.  There are more categories for scientific, video, games, medical and more.  The following list shows most of the formats used in common email.

 

3DS       3D Studio
 8BF      Adobe Photoshop
 AAC      Advanced Audio Coding (Mac)
 APP      Apple Executable
 AFM      Adobe font metrics (Type 1)
 AI        Adobe Illustrator graphics,
 AIF       Digital audio (Mac)
 AIFC     Digital audio (Mac)
 AJAX     Asynchronous JavaScript And XML
 ALB      JASC Image Commander
 ANI      Animated cursor
 ANN     Windows help annotations
 ANS      ANSI text
 ARC      ARC, ARC+ compressed archive
 ASA      ASP info
 ASAX    ASP.NET file
 ASC      ASCII file
 ASCX    ASP.NET file
 ASD      Word temporary document
 
 ASMX    ASP.NET file
 ASP      Active Server Page
 ASPX    ASP.NET file
 ATT      AT&T Group IV fax
 AU        Digital audio (Sun)
 AVI       Microsoft movie format
 BAK      Backup
 BAS      BASIC source code
 BAT      DOS, OS/2 batch file
 BIN      Driver, overlay
 BML      Bookmark library (SyncURL)
 BMP      Windows & OS/2 bitmap
 BMK     Windows help bookmarks
 C         C source code
 CAB      Microsoft compressed format for distribution
 CAL      Windows calendar,
 CCB      Visual Basic animated button
 CDA      CD audio track
 CDX      FoxPro and Clipper index
 CFG      Configuration
 CGM     CGM vector graphics
 CHK      DOS/Windows corrupted file (Chkdsk)
 CIT       Intergraph scanned image
 COB      COBOL source code,
 COB      Truespace 3-D file
 CLP      Windows clipboard
 CLS      Visual Basic class module
 CMP      JPEG bitmap, LEAD bitmap
 CMP      RichLink composed format
 CNT      Windows help contents
 COM     Executable program
 CPD      Fax cover document
 CPE      Fax cover document
 CPI       DOS code page
 CPL      Windows control panel applets
 CPP      C++ source code
 CPR      Knowledge Access bitmap
 CRD      Cardfile file
 CSV      Comma delimited
 CUR      Cursor
 CUT      Dr. Halo bitmap
 CV5      Canvas 5 vector/bitmap
 DAT      Data
 DB       Paradox table
 DBF      dBASE database
 DBT      dBASE text
 DCA      IBM text
 DCM     DICOM medical image
 DCS      Color separated EPS format
 DCX      Intel fax image
 DCT      Dictionary
 DEF      Definition
 DIB      Windows DIB bitmap
 DIC      Dictionary
 DIF       Spreadsheet
 DISCO   Publishing and Discovering Web Services
 DLG      Dialogue script
 DLL      Dynamic link library
 DOC     Microsoft Word Document (2003-2007)
 DOCX    Microsoft Word Document (2008-)
 DOT      Microsoft Word template
 DPI       Pointline bitmap
 DRV      Driver
 DWG     AutoCAD vector format
 DX       Autotrol document imaging
 DXF      AutoCAD vector format
 ED5      EDMICS bitmap (DOD)
 EMF      Enhanced Windows metafile
 EPS      Encapsulated PostScript
 EXE      Executable program
 FAX      Various fax formats
 FLC      Autodesk animation
 FLI       Autodesk animation
 FLT       Graphics conversion filter
 FMT      dBASE Screen format
 FMV      FrameMaker raster & vector graphics
 FNT      Windows font
 FOG      Fontographer font
 FON      Windows bitmapped font,
 FON      Telephone file
 FOR      FORTRAN source code
 FOT      Windows TrueType font info.
 FPX      FlashPix bitmap
 FRM      dBASE report layout
 FTG      Windows help file links
 FTS      Windows help text search index
 GDF      GDDM format
 GED      Arts & Letters graphics
 GEM     GEM vector graphics
 GID      Windows help global index
 GIF       CompuServe bitmap
 GP4      CALS Group IV - ITU Group IV
 GRA      Microsoft graph
 GRP      Windows ProgMan Group
 GZ       UNIX Gzip
 H         C header
 HED      HighEdit document
 HGL      HP Graphics language
 HLP      Help text
 HPJ       Visual Basic help project
 HPP      C++ program header
 HPL      HP Graphics language
 HT        HyperTerminal
 HTM      HTML document (Web page)
 HTML    HTML document (Web page)
 HTX      HTML extension file
 ICA       IBM MO:DCA - IOCA bitmap
 ICO      Windows icon
 IDC      Internet Database Connector
 IDD      MIDI instrument definition
 IDE       Development environment configuration
 IMG      Macintosh image file
 IMG      GEM Paint bitmap
 INF       Setup information
 INI       Initialization
 JAR      JAVA data

 JFF       JPEG bitmap
 JIF       JPEG bitmap
 JPG      JPEG bitmap
 JS        JavaScript file
 JT        JT Fax
 JTF       JPEG bitmap
 KDC      Kodak Photo bitmap
 KFX      Kofax Group IV fax
 LBL       dBASE label
 LEG      Legacy text
 LIB       Function library
 LIT       Microsoft Reader file
 LOG      Log file
 LQT      Liquid Audio
 LSN      Topic list (CDE)
 LST      List
 LV        LaserView Group IV
 M1V      MPEG file
 M3U      MPEG file
 MAC     MacPaint bitmap
 MAK     Visual Basic/MS C++ project
 MAP      Link editor map
 MBX     Mailbox (e-mail)
 MCS     MathCAD format
 MCW     Word for Macintosh document
 MDB     Access database
 MDF     Mircrosoft SQL server database

 MET      OS/2 Metafile
 MEU      Menu items
 MDX     dBASE IV multi-index
 MID      MIDI sound file
 MME     MIME-encoded file
 MMF     Microsoft mail file
 MMM     Macromind animation format
 MOD     Eudora script file
 MOV     QuickTime movie
 MPA      MPEG file
 MP2      MPEG file
 MP2V    MPEG file
 MP3      MPEG-1 Layer 3 audio
 MPE      MPEG file
 MPEG    MPEG file
 MPG     MPEG file
 MPP      Microsoft Project
 MSG     Message file
 MSP      Microsoft Paint bitmap
 MUS     Music
 MVB     Microsoft Multimedia Viewer
 MYD     MYSQL table data

 MYI      MYSAM table index

 M1V      MPEG file
 NAP      NAPLPS format
 NDX     dBASE index
 NDX     CDE index
 NG       Norton Guides text
 NLM      NetWare NLM program
 O         UNIX machine language
 OAZ      OAZ Fax
 OBD     Microsoft Office binder
 OBJ      Machine language,
 OBJ      Wavefront 3-D file
 OBZ      Microsoft Office wizard
 OEB      Open eBook publication
 OPF      Open package file
 ORG     Organizer file
 OTF      OpenType font
 OVL      Overlay module
 OVR      Overlay module
 OUT      Encyclopedia definitions
 P10      Tektronic Plot 10
 PAL      Windows palette
 PAS      Pascal source code
 PBD      PowerBuilder dynamic library
 PBK      Microsoft Phonebook
 PBM      Portable Bitmap
 PCL      HP LaserJet series
 PCD      Photo CD bitmap
 PCM      LaserJet cartridge information
 PCS      PICS animation
 PCT      PC Paint bitmap,
 PCT      Macintosh PICT bitmap & vector graphics
 PCW     PC Write document
 PCX      PC Paintbrush bitmap
 PDF      Portable Document Format (Acrobat),
 PDV      PC Paintbrush printer driver
 PFA      Type 1 font (ASCII)
 PFB      Type 1 font
 PFM      Windows Type 1 font metrics
 PIC       Vector formats
 PIC       Mac PICT format
 PIC       IBM Storyboard bitmap
 PIF       Windows info. for DOS programs,
 PIF       IBM Picture Interchange
 PL        Perl script
 PLT       AutoCAD plotter file
 PLT       HPGL plotter file
 PNG      PNG bitmap
 POV      POV-Ray ray tracing
 PPD      PostScript printer description
 PPM      Portable Pixelmap
 PPS      PowerPoint Slideshow
 PPT      PowerPoint
 PRD      Microsoft Word printer driver
 PRG      dBASE source code
 PRN      Temporary print file
 PRT      Formatted text
 PS        PostScript page description
 PSD      Photoshop native format
 PST      Microsoft Outlook file

 PUB      Microsoft Publisher publication,
 PUZ      Crossword puzzle
 PVK      Private Key
 PWL      Windows password list
 QBW     QuickBooks
 QLB      Quick programming library
 QT        QuickTime movie
 QTM     QuickTime movie
 RA        Real Audio file
 RAM     Real Audio file
 RAS      Sun bitmap
 RAW     3-D file (open standard)
 RC        Resource script
 REC      Recorder file
 REG      Registration file
 RFT      DCA/RFT document
 RIA       Alpharel Group IV bitmap
 RLE      Compressed

 RM       Real Media file
 RMI      MIDI music
 RMM     Real Media file
 RNL      GTX Runlength bitmap
 RTF      Rich-text format (Microsoft)
 RV        Real Video file
 SAT      ACIS 3-D model
 SAV      Saved file
 SBP      IBM Storyboard graphics/Superbase text
 SC2      Microsoft Schedule+ 7
 SCD      Microsoft Schedule+ 7
 SCH      Microsoft Schedule+ 1
 SCM     ScreenCam movie
 SCP      Dial-up Networking script
 SCR      Windows screen saver
 SCR      Fax image
 SCR      dBASE screen layout,
 SET      Setup parameters
 SLD      AutoCAD slide
 SND     Digital audio
 SWF     Shockwave file
 SYS      DOS, OS/2 driver
 TAL      Adobe Type Align shaped text
 TAR      Tape archive
 TAX      TurboTax

 TAZ      UNIX Gzip archive
 TGZ      UNIX Gzip archive
 TIF       TIFF bitmap
 TLB      OLE type library
 TMP      Temporary
 TOC      Table of contents
 TRM      Terminal file
 TTC      TrueType font compressed
 TTF      TrueType font
 TXT      ASCII text
 VCF      vCard file
 VOC      Sound Blaster sound
 VOX      Voxware compressed audio
 VSD      Visio drawing
 VUE      dBASE relational view
 WAV     Digital Audio (Windows)
 WAX     WMA metafile (location of WMA file)
 WBK     Microsoft Word backup
 WBT     WinBatch file
 WDB     Microsoft works data file
 WIF      Wavelet image
 WIZ      Microsoft Word wizard
 WMA     Windows Media Audio (ASF file)
 WMF     Windows Metafile
 WMV     Windows Media video (ASF file)
 WPS     Microsoft Works document
 WRI      Windows Write document
 WRL     VRML page
 WSH     Windows Scrip Host properties
 WVL     Wavelet compressed file
 WVX     WMV metafile (location of WMV file)
 XBM     X Window bitmap
 XFX      JetFax
 XLA      Excel add-in
 XLB      Excel toolbar
 XLC      Excel chart
 XLD      Excel dialogue
 XLK      Excel backup
 XLM      Excel macro
 XLS      Excel spreadsheet
 XLT      Excel template
 XLW     Excel project
 XML      XML file
 XPM      X Window pixelmap
 XSD      XML schema
 XWD     X Window dump
 Z         UNIX Gzip archive
 ZIP       PKZIP compressed
 $$$      Temporary