RESOLVED! Removing the "SendCharset=0" entry from Eudora's INI file solved this problem.

I cannot get any mail from my client [Eudora (7.1.0.9)] to make it to my mother's new Presto printer. All attempts, even one with nothing but one attached .JPG, get dumped with a Presto Bulletin rejecting the messages for "unsupported formatting" with no clue as to what specifically is the problem.

In order to help pinpoint the problem, I was able to use a web-based client to finally get *something* to the printer in question. An analysis of that successful message vs. rejected versions [as captured via CC:s to another account] is available at http://d2.gap.net/Misc/PrestoFormatRejectionProblem.pdf.

As explained in the analysis that one instance has been narrowed to a very few possibilities within the headers. If I were to know specifically what is causing the problem [the Presto Bulletins should quote the portion of messages that have been rejected for this and, probably, other causes] I could likely implement some kind of effective work-around.