704 messages fall into this category. Of these, 596 come from a single (malfunctioning and duplicate spewing) list server. I have not yet examined the remaining 208 messages, but I'll bet anything many also have duplicate message bodies. Or are spam. So for this data set, we have an upper bound of 0.01% messages in this category, possibly significantly less.
Correction.
... remaining 108 ... 0.005% ...