Re: MIME Filters

1996-04-26 03:03:00
At 12:43 26/04/96 +1000, you wrote:
Did you take a look at the output of MHonArc of what used to be your Word
document? Is it 7 bit ASCII, 8 bit binary, 6 bit base64 or something else?
You've put your finger on the right problem, it's a file format discrepancy.
The file stored on the Unix server is not recognised by Word as a valid

The first thing I would try would be to send a program file to MHonArc, then
download it using your WWW-browser. Start the copied program to see if it
works, and see if the copy has the same length as the original.

My bet is that the above will work. Now do the same thing with a .doc file.
Compare the two using Dos's 'fc -b file1 file2'. View the files using a hex
to find out where exactly things were altered.

If it doesn't work, you may have not configured Eudora properly, check

I'm not very familiar with the fomats you mentioned, I mean I've heard the
a million times but I don't think I could write a script that does conversions
between those types. Any advice as to where I could find information about
that ?
Naturally if you would be so kind as to explain the basics to me, I'd be 
delighted :-)

From what I understand :

8-bit files use all the bits that there are to a byte.
7-bit files do not use the most significant bit, which is always set to 0.
6-bit files do not use the 2 most significant bits, which are set to 0.

Some older gateways will not allow for 8-bit to go through, they are not
"8-bit-clean". The conversion they do is simple: they set the (2) most
significant bit(s) to some value, most of the time 0. This is not reversible

Now, uuencode and MIME base64-encoding (basically) do a reversible mapping
of 8-bit code to 6-bit code. You will notice that uuencoded files are 4/3
larger than their binary counterparts. The extra space has been used to
store the 2 most significant bits in a way that renders them immune to evil
gateways. In fact, the two use different mapping alphabets, as you might
glance in that comes with mhonarc. 

You then send the 6-bit file using any mailer, and it will pass any gateway,
because the 2 most significant bits are insignificant when it comes to the
content of the message; they may thus be altered. At the receiving end, the
file is reconstructed. 

Some mailers (Eudora) automate this processing : When you send a file using
"Attachments", Eudora (if configured properly) encodes it with base64, and
then incoporates it into the body of the email using MIME conventions. The
other party then decodes it, extracts and saves the file, replacing the part
of the mail it occupied by something like
        Attachment converted : C:\stuff\eudora\snafu.ext

Thanks for your help,

You're welcome. Gotta get back to my work.

Ulrich Kroener <ulrich(_at_)eiba(_dot_)com>

         E I B A s.c. - Av. de la Tanche 5, B-1160 Brussels
        tel.: +32 2 675 50 20 - fax: +32 2 675 50 28

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