Apple Mail

There really is no “Macintosh Format”, but there sure are a lot of formats you only find on the MacOS. From Resource Forks and iWork formats to unique sound formats, MacOS has them all! Majority of cross-platform software vendors have done a much better job in recent years in making their file formats the same across platforms, but for Apple, they love to make things unique, just for their platform.

Take EMLX for example. Seems to be a trend to add “X” to the end of an older format to breath new life into it. The EML format, or Electronic Mail, has existed for a few decades now, but in 2005 Apple updated their Apple Mail application to use a new format, EMLX.

As far as I know, Apple hasn’t released any documentation on the EMLX format, but many folks out there have asked the question and have been able to “reverse engineer” the format. Lets take a look.

An EMLX file consists of three parts:

  • bytecount on first line;
  • email content in MIME format (headers, body, attachments);
  • Apple property list (plist) with metadata.

The bytecount is a variable number which consists of the total bytes starting from the start of the MIME format, including HTML, to the start of the XML property list. Lets look at a simple EMLX.

The byte count is on line 1 with the MIME email (EML) taking up the 556 bytes, then the XML plist at the end. You may ask, what is a plist? Well, it is another Apple (originally NextStep) invention which is embedded throughout the MacOS operating system. A Plist is usually an XML with keys but can also be in a binary format. The Plist can contain properties of the email within Apple Mail like special color flags, tagged as junk, date received and last reviewed.

If you do happen across an EMLX file or group of them, there are a few tools you can use to convert them to a plain old EML. There are python libraries or many other tools to do the job.

But first we need to be sure of identification beyond the extension. Adding this file format to PRONOM would help in identification for preservation purposes. If ran through PRONOM today we get:

filename : '9.emlx'
filesize : 18582
modified : 2023-10-26T22:16:25-06:00
errors   : 
matches  :
  - ns      : 'pronom'
    id      : 'fmt/950'
    format  : 'MIME Email'
    version : '1.0'
    mime    : 'message/rfc822'
    class   : 'Text (Structured)'
    basis   : 'byte match at [[31 17] [599 4] [339 6] [426 6] [90 14]]'
    warning : 'extension mismatch'

Because the format has a EML plain text format within its structure, it is assumed to be an EML file. While technically accurate, Identifying as a unique EMLX format would be beneficial in a preservation system so you can properly assign risk and choose the right tool to parse or migrate.

In looking at the three parts of an EMLX format, we know the EML file is not a good way to show the difference as they are the same structure. The byte count on the first line is variable, so there is no static byte sequence to use for identification. That leaves the Plist section at the end to distinguish the difference.

The PRONOM entry for a Plist looks for the typical XML strings present in most XML files, but then uses the root element “<plist version=”1.0″>” for identification. We could combine the existing EML signature and the Plist signature to identify an EMLX, or just take the existing EML signature and put in a small byte sequence for the closing of the </plist> tag near the EOF? There would be a need for a priority over EML, both would essentially accomplish the same thing.

Take a look at latter idea on my GitHub page and tell me which makes the most sense.

Common Ground

If digital preservation had an extension it most likely would be .DP

Unfortunately, it’s taken. Say hello to Digital Paper.

In the early 1990’s, folks started to share documents with each other through the their phone lines. The early internet, BBS, AOL, CompuServe and the like allowed people to share ideas through applications like Word/WordPerfect Documents. Most people had a copy of the popular software and that software could open documents from their competitors, but fonts were always a problem. Technically a font is software as well and needs a license to be used. Also printers at the time dictated what the document might look like when opened, so your document may look different on someone else’s computer. This lead to a few innovations in the software market Digital Paper.

The idea is simple, create a format which could be opened with a free viewer which includes all the parts to make it look and print just like it was intended to. You may have already guessed who the winner in this space tuned out to be, yes, the PDF format. You can’t tell the history of the PDF Format without mentioning others that tried their luck to be the leader in portable document formats . WordPerfect’s Envoy format was one, Common Ground Digital Paper was another.

No Hands Software which started in 1990, developed the idea of making your documents truly portable. They released the Common Ground Maker and Viewer software in 1993. By 1996 the company was doing so well they were bought for $6 million by Hummingbird Ltd. PDF soon became so ubiquitous, formats like Common Ground and Envoy fizzled out. That doesn’t mean they didn’t have a big impact and still can be found in quite a few places.

Apple was one of the bigger users for awhile, but the format can still be found floating around today.

The Common Ground Digital Paper has some similarities to the PDF format, but the biggest different is the format is proprietary and not open like PDF. Another difference is you could embed the viewer into the file, this would make an executable on both Windows and Macintosh. Very convenient for sending to those who may not have the viewer or can’t install the viewer on their system.

Common Ground had two different viewers, a pro viewer with more features and a Mini Viewer with basic features and which was free to download and distribute from their website. Unfortunately, they linked to an FTP site which no longer is available and so finding the viewers today can be difficult.

I came across a boxed version 1 for Macintosh of the software a few years back, but have yet to find other full versions. The software did change hands a bit, but seems to have topped out at Version 4 in the late 1990’s. Let’s take a look at the file format for the samples we do have.

Version 1 for the Macintosh was the first I believe, coming to Windows shortly afterwards. The format was even assigned a MimeType for use on the web and the application gives us a little insight into the format.

The commonground file format does have versions (two at the moment). They *are* internally documented with a file signature, allowing commonground viewers to automatically handle both old and new format files. Therefore, I don’t believe a ‘version’ parameter is needed.

A Content-Type of “application/commonground” indicates a document in the Common Ground portable file format, also known as Digital Paper.

Encoding considerations: Common Ground files are in a binary format. Some encoding will be necessary for MIME mailers as in application/octet-stream. Common Ground files for the Macintosh are encoded in the data fork of a Macintosh file. The file type is APPL, the creator is CGVM.

If we look at a sample from Version 1 for the Macintosh we find the follow hex values:

hexdump -C CG-s01.dp | head
00000000  00 00 03 56 00 00 04 d9  43 47 44 43 00 00 00 00  |...V....CGDC....|
00000010  96 6c 00 07 04 b4 03 de  00 00 00 00 02 da 02 28  |.l.............(|
00000020  00 11 02 ff 0c 00 ff ff  ff ff 00 00 00 00 00 00  |................|
00000030  00 00 02 28 00 00 02 da  00 00 00 00 00 00 00 01  |...(............|
00000040  00 0a 00 05 00 05 00 15  02 23 00 32 00 05 80 02  |.........#.2....|
00000050  00 15 7f fe 00 2c 00 09  00 03 06 47 65 6e 65 76  |.....,.....Genev|
00000060  61 00 00 03 00 03 00 0d  00 0c 00 2e 00 04 00 00  |a...............|
00000070  00 00 00 2b 06 11 07 54  65 73 74 69 6e 67 00 01  |...+...Testing..|
00000080  00 0a ff e1 ff e2 02 f9  02 46 00 03 00 00 00 0d  |.........F......|
00000090  00 00 00 28 02 d5 01 05  05 2d 20 31 20 2d 00 ff  |...(.....- 1 -..|

In all the samples I have the first 8 bytes are not consistent, but the next four bytes are. CGDC, which happens to be the registered type on the Macintosh. Convenient. But it appears later versions are not the same.

hexdump -C MANUAL.DP | head
00000000  00 00 00 20 00 00 b7 f4  44 50 4c 33 00 00 00 04  |... ....DPL3....|
00000010  00 00 00 00 00 00 00 00  3b 60 53 df 00 00 00 00  |........;`S.....|
00000020  00 00 00 18 00 00 b4 da  00 00 b4 c2 00 00 03 3e  |...............>|
00000030  78 00 79 00 7a 00 7b 00  00 00 00 77 01 01 00 0c  |x.y.z.{....w....|
00000040  00 01 02 01 00 00 00 97  fe ed f0 05 00 b7 86 04  |................|
00000050  5f 05 f7 01 00 03 ed f0  02 00 3d 00 ff 45 75 72  |_.........=..Eur|
00000060  6c 20 00 01 07 ff bf 05  9f 00 01 08 a3 05 fb ba  |l ..............|
00000070  02 fa f1 00 ff ff 00 11  ff 68 74 74 70 3a 2f 2f  |.........http://|
00000080  77 ff 77 77 2e 47 53 50  2e 43 b9 43 1c 0f 03 04  |w.ww.GSP.C.C....|
00000090  95 05 c8 0d 00 cc fb 05  e3 13 06 15 6d 61 69 6c  |............mail|

hexdump -C dpwhite.dp | head
00000000  00 00 00 18 00 01 79 17  44 50 4c 32 00 00 00 00  |......y.DPL2....|
00000010  00 00 00 00 00 00 00 00  00 00 00 18 00 01 76 de  |..............v.|
00000020  00 01 76 c6 00 00 04 b2  00 00 00 00 00 00 00 00  |..v.............|
00000030  00 00 00 1e 01 01 00 0c  00 00 01 01 00 00 00 12  |................|
00000040  00 01 00 01 00 00 00 00  0c 4e 09 60 01 2c 01 2c  |.........N.`.,.,|
00000050  00 64 00 00 00 02 00 00  00 00 00 a2 01 01 00 0c  |.d..............|
00000060  00 01 02 01 00 00 00 e2  fa ed f0 22 ed f1 0c 4e  |..........."...N|
00000070  09 60 00 ff e1 01 26 0a  83 08 3b ff ff 6a ff 6a  |.`....&...;..j.j|
00000080  0c e4 09 f6 01 ff 2c 01  2c 00 08 00 64 00 df 00  |......,.,...d...|
00000090  01 01 00 03 ed f0 0f 00  79 0a 1c 0f 28 07 42 41  |........y...(.BA|

These files are from a later version and have a different string at byte 8. DPL2 & DPL3. In the MiniViewer you can request document information and it provides some basic metadata for each file.

I only have one example of the DPL3, but a couple examples of DPL2, and it seems like DPL2 comes from a Version 3 DP Maker and DPL3 comes from Version 4 Maker. Need to see if I can find a Version 2 file and see if it follows the same pattern.

Two of my favorite CD-ROM’s on Internet Archive are Dr. Dobb’s The Essential Books on File Formats and Internet File Formats, both have copies of the Mini Viewer.

One of features similar to PDF is the ability to password protect certain features. This is what the document information looks like.

The header is the same, but the plain text usually seen in the file is no longer visible, so it appears the rest of the file is encrypted.

hexdump -C password.dp | head 
00000000  00 00 5d 95 00 00 06 94  43 47 44 43 00 00 00 01  |..].....CGDC....|
00000010  8e 3b 18 7e c5 16 f8 e0  0f f5 6f 32 2f 34 36 81  |.;.~......o2/46.|
00000020  4b 8a 03 da 9e 1a 85 6c  36 e4 39 f2 5a 2a a2 5f  |K......l6.9.Z*._|
00000030  81 83 65 ee 9c 16 d0 2d  2d c3 04 df 69 c8 06 0d  |..e....--...i...|
00000040  77 df 27 19 33 59 f6 05  61 4e 2c a6 58 27 47 26  |w.'.3Y..aN,.X'G&|
00000050  fe 6b 3c 06 7e cb 7f fb  33 f8 64 ed 05 54 b4 7d  |.k<.~...3.d..T.}|
00000060  c7 b5 e3 c2 df 40 53 63  ef 8e 10 1c c7 58 bd 28  |.....@Sc.....X.(|
00000070  9b 8a 2c 8f ae 82 33 f7  ff d4 3c 96 5c b4 08 69  |..,...3...<.\..i|
00000080  1f 00 af ce a7 56 93 27  07 cc 39 97 17 22 49 d7  |.....V.'..9.."I.|
00000090  5b 89 9b e6 b7 b1 5c 38  75 ba 08 ee 66 d0 9a d2  |[.....\8u...f...|

This file format is not currently in PRONOM. From what I have gathered I could add three signatures. There could be some other variations out there and the password protection needs to be considered. Maybe I’ll take Nick Gault’s offer and request the format which was available starting in the middle of 1995. Think they’ll deliver?

No bad deed….

I had access to my first Macintosh computer around 1987. My father brought it home and I spent hours on it playing games and occasionally writing reports for school. The Macintosh Plus computer had one floppy drive and no hard drive. I remember playing the game Orbiter which had two floppy disks and right in the middle of game play it would pause and ask me to insert disk 2, then quickly ask for disk 1 again. The struggle was real. I spent years using many different Macintosh computers and now own more than I wish to admit. I’m preserving them!

The wild world of digital preservation has been a little lacking on the Macintosh side of things as I have come to realize. There still not a great way to manage Resource Forks in many preservation systems and the identification tools are mainly focused on the data bytetreams and not any system specific attributes Macintosh used often.

The PRONOM registry has either referenced early Macintosh specific formats or missed them entirely so I have been slowly working on a few to close that gap.

Interestingly enough, many Microsoft programs initially made their GUI debuts on the early Macintosh before making their way to Windows. Excel is one I am working on, as Version 1 is not identifiable in PRONOM, it was Macintosh only at the time.

Another is PowerPoint, I recently submitted two new signatures to PRONOM.

fmt/1747: Microsoft PowerPoint Presentation v2.x. Full entry added.
fmt/1748: Microsoft PowerPoint Presentation v3.x. Full entry added.
fmt/1866: Microsoft Powerpoint for Macintosh v.2. Full entry added.
fmt/1867: Microsoft Powerpoint for Macintosh v.3. Full entry added.

PowerPoint was initially released in 1987 on the Macintosh platform. It was developed by a company called ForeThought. Version 1.0 on the Macintosh was under this name, until it was bought by Microsoft only three months after being released. The history of PowerPoint can be discovered at Robert Gaskins, one of the original developers, website and book he wrote. The available information provided by Microsoft is only for the OLE format, covering versions 4.0 until 2003.

So, lets take a look at the Powerpoint original file format, before OLE.

   Type/Creator      RF      DF  Date         Filename
f  SLDS/PPNT         0       932 Oct 10 19:10 PowerPoint-v1

Luckily the early PowerPoint files did not have a Resource Fork. The Data Fork, if you haven’t noticed, has an interesting set of hex values at the beginning of the file. 0BADDEED is the first 4 bytes. If we look at a PowerPoint version 2 file from Windows.

The file format is the same, but because of the weird world of endianness, the first few bytes are in reverse order, EDDEAD0B.

Obviously we need to discuss this magic number and the meaning behind “Bad Deed”. This question was asked previously by the digital preservation community. I have a previous blog post about the use of words for the magic number CAFEBEEF as it was used with with JAVA class files and Express Publisher in the 1990’s. BADDEED looks like another clever use of the hex values that formed words. But was there a story behind the words? Joe Carrano asked if this string might be hexspeak. I wanted to know more so I asked some one who might know.

Robert Gaskins was kind enough to chat with me for a bit about the early days of PowerPoint.

I had a theory on the possible meaning behind BADDEED, so I asked him what the feeling was like between Apple and Microsoft at the time. I had heard for years that PowerPoint was originally created for the Macintosh, but Robert informed me:

  In fact, PowerPoint was designed first for Microsoft Windows, 

and its first spec shows that: “All the screen shots, menus, and 

dialogs were set up to look like Microsoft Windows, not like 

Macintosh.”  (Gaskins, Sweating Bullets, p. 92)  You can see that 

spec here.

A year later, we concluded that we would be forced to ship 

on Mac first, although we still thought that Windows was the 

big opportunity and thought that Mac was risky.  “We just didn’t think 

we could successfully ship a product for Windows, yet, though we planned 

to later. (Gaskins, Sweating Bullets, p. 105)  The considerations are 

summarized in my June 1986 product marketing document.

Of course, we turned out to have been right all along.  PowerPoint on 

Mac was much loved, but sales remained poor because Mac sales were 

so poor.  It was only after we shipped on Windows that PowerPoint gained 

the dominant market share which has characterized it ever since, and 

Windows PPT outsold Mac PPT very quickly. (Gaskins, Sweating Bullets, p. 403)

So my original thought was that there was some bad feelings around this Apple, Microsoft battle which has been the sentiment for quite some time. So when I asked if any of that influenced the use of BADDEED, I was told:

So, far from being disgruntled by expanding PowerPoint to Windows, 

that had been our goal all along, and its achievement was the most 

important success we had.

I judge that you are fully aware of all that, and that 

your question is more, “was there any bad deed signified 

by the Mac hex value chosen?”  No, it was just the poverty 

of choice when you only have six letters.

So there you have it. The use of the hex values 0x0BADDEED, was simply chosen from a limited set of values when looking at words hexadecimal could spell. I guess I should never let the truth get in the way of a good story.

I continued to have a wonderful conversation with Robert and also asked him for some details on the rest of the PowerPoint file format. I was hoping there might be some documentation out there explaining the early format before Microsoft took over. Robert said:

 I don’t know of any such documentation apart from the official 

Microsoft support files available online.  I don’t have any such 

information.  I know that Dennis Austin deposited some of our 

working files at the Computer History Museum (not online):

and it’s likely that some information is there–if nothing 

else, it claims to contain a source code listing for PPT 1.0 

which would contain the code to read the file format.

So there might be some information in at the Computer History Museum worth looking into.

As far as I could tell from the available online information, there is a few differences between Version 1.0 and Version 2.0, the biggest being the fact that 1.0 did not have an option to print in color, amount a few other minor things. Here is a screenshot of a page from the Microsoft PowerPoint 2.0 documentation on

I suppose with the signature additions of the Macintosh and Windows versions 2.0 and 3.0 of the PowerPoint file format in PRONOM, that should cover most needs. Currently my PowerPoint 1.0 files identify at 2.0 files, so I may need to have them adjust the PUID to include both versions 1.0 and 2.0 as they are so similar. If I am able to find a difference or get my hands on the original source code I may find a better solution.

Quicktime MooV

During the 1990’s Apple Quicktime became the dominant digital media standard. It is the basis for the MPEG-4 format which is used everywhere now. Technically the Quicktime Movie format is a container or wrapper which can hold a variety of Video and Audio streams.

The basic unit of a Quicktime Movie is an atom. The MooV atom is the most important piece of a Quicktime Movie. Without it and the “mvhd” header atom, all the characteristics of the movie are lost.

Having the MooV atom missing from your movie file seems like it would be a rare thing, but it may happen more often than you think.

What happens when you come across a Quicktime file on an HFS disk, like one of these:

If you try and open the movie you might see this.

MediaInfo doesn’t know what to make of the file. You can see the hex values from the beginning of the file, there clearly is no MooV atom.

Enter Macintosh Resource Forks.

Original Quicktime files stored the MOOV atom in a resource fork.

Lets take a look a closer look at one of these files.

derez Wildebeest 
data 'moov' (128) {
	$"0000 0465 6D6F 6F76 0000 006C 6D76 6864"            /* ...emoov...lmvhd */
	$"0000 0000 E143 7EF5 E143 7EF5 0000 0258"            /* ....?C~??C~?...X */
	$"0000 1068 0001 0000 00FF 0000 0000 0000"            /* ...h.....?...... */
	$"0000 0000 0001 0000 0000 0000 0000 0000"            /* ................ */
	$"0000 0000 0001 0000 0000 0000 0000 0000"            /* ................ */
	$"0000 0000 4000 0000 0000 0000 0000 0000"            /* ....@........... */
	$"0000 0924 0000 0000 0000 0000 0000 0000"            /* ...$............ */
	$"0000 0002 0000 03D9 7472 616B 0000 005C"            /* .......?trak...\ */
	$"746B 6864 0000 000F A5EA 1D89 E143 7EF5"            /* tkhd....??.??C~? */
	$"0000 0001 0000 0000 0000 1068 0000 0000"            /* ...........h.... */
	$"0000 0000 0000 0000 0000 0000 0001 0000"            /* ................ */
	$"0000 0000 0000 0000 0000 0000 0001 0000"            /* ................ */
	$"0000 0000 0000 0000 0000 0000 4000 0000"            /* ............@... */
	$"00A0 0000 0078 0000 0000 0024 6564 7473"            /* .?...x.....$edts */
	$"0000 001C 656C 7374 0000 0000 0000 0001"            /* ....elst........ */
	$"0000 1068 0000 0000 0001 0000 0000 0351"            /* ...h...........Q */
	$"6D64 6961 0000 0020 6D64 6864 0000 0000"            /* mdia... mdhd.... */
	$"E143 7EF5 E143 7EF5 0000 0258 0000 1068"            /* ?C~??C~?...X...h */
	$"0000 003C 0000 003A 6864 6C72 0000 0000"            /* ...<...:hdlr.... */
	$"6D68 6C72 7669 6465 6170 706C 4000 0000"            /* mhlrvideappl@... */
	$"0001 002C 1941 7070 6C65 2056 6964 656F"            /* ...,.Apple Video */
	$"204D 6564 6961 2048 616E 646C 6572 0000"            /*  Media Handler.. */

The MooV atom is in the Resource Fork. Apple explains why they did it this way.


Note: the header is safer when stored at the beginning of the file or in the HFS resource fork as type ‘moov’; ID any. The advantage of using another file fork is that the header can be lengthened without recalculating the sample offsets or new header must be written at the end of the file.


If you are playing back a movie on an older Macintosh using an earlier version of Quicktime, you won’t have any issues, but if you plan on playing the movie on a newer system or try and preserve the file, then we run into problems. Especially if the file is moved off of the HFS disk onto a system which doesn’t maintain the resource fork. Then you are stuck with just the data with no way to interpret the movie file.


One solution you can follow is to use MacBinary or AppleSingle to combine the Resource Fork and Data Fork together into one file. You are left with a different format, but one which can be preserved and reverted back to the original when needed.

Another way is to create a Single-Fork Movie file, aka a normal QuickTime file.

“single-fork movie file – A QuickTime movie file
that stores both the movie data and the movie
resource in the data fork of the movie file. You
can use single-fork movie files to ease the
exchange of QuickTime movie data between
Macintosh computers and other computer

Inside Macintosh – QuickTime

Creating a Single-Fork can be accomplished a couple different ways. One is to use an older version of QuickTime to “Save As” to a self contained file with the box checked to allow playback on a “non-Apple” computer.

Another method is to use a simple utility called Single Fork Flattener. I found a copy on a old QuickTime disc and uploaded to Macintosh Garden if you want to try it out. No QuickTime needed, just open the file and it updates it to include the MooV resource. Also a tool called FlattenMooV.

Once combined, MediaInfo now sees a complete QuickTime file which VLC can play!

mediainfo Wildebeest2 
Complete name                            : Wildebeest
Format                                   : QuickTime
Format/Info                              : Original Apple specifications
File size                                : 565 KiB
Duration                                 : 7 s 0 ms
Overall bit rate                         : 661 kb/s
Frame rate                               : 10.000 FPS
Encoded date                             : 2023-10-02 14:15:15 UTC
Tagged date                              : 2023-10-02 14:15:15 UTC
Writing library                          : Apple QuickTime
FileExtension_Invalid                    : braw mov qt

ID                                       : 0
Format                                   : Road Pizza
Codec ID                                 : rpza
Duration                                 : 7 s 0 ms
Bit rate                                 : 659 kb/s
Width                                    : 160 pixels
Height                                   : 120 pixels
Display aspect ratio                     : 4:3
Frame rate mode                          : Constant
Frame rate                               : 10.000 FPS
Bits/(Pixel*Frame)                       : 3.434
Stream size                              : 563 KiB (100%)
Language                                 : English
Encoded date                             : 1992-03-16 09:40:25 UTC
Tagged date                              : 2023-10-02 14:15:15 UTC

I was hoping I could find a method to use a modern tool to combine into a Single-Fork file, but nothing yet. I did find a C++ source that when compiled does indeed merge the two forks together, which in this case merges the MooV atom at the end of the file. Its called qtmerge. QuickTime 7 is your best bet for a GUI tool which works on recent MacOS, but not the last couple versions. There is a reference out there to a tool called RezWack, but I have been unable to verify.