Tested with Outlook Express 6.0 and mutt 1.3.25i...
What concerns mutt: it decides, whether to use base64 or q-p as follows:
If Mutt can not determine the mime type by the extension of the file
you attach, it will look at the file. If the file is free of binary
information, Mutt will assume that the file is plain text, and mark it
as text/plain. If the file contains binary information, then Mutt
will mark it as application/octet-stream.
At first, there was no dbf extension in mime.types, which I added to application/octet-stream and mutt understood that. But the encoding for some dbf's remains q-p (as mutt finds, that the file does not contain binary information ;), but it does, and apparently there is a problem.
And about outlook, I suppose, it uses similar algorithm, because some dbf's
are attached as base64 and some as q-p, depending on data in them (if there are any char fields).
On 02 01 16, Donna Harris wrote:
> It's very strange that a mail client is encoding a .dbf file
> as quoted-printable since quoted-printable is only applicable
> for MIME types of text/* (and I would expect a .dbf file
> to be of type application/dbf or something similar).