Brief update:
Today I received what I assume is another bogus e-mail with an attachment from whoever is pretending to be xl7-owner. The subject started with the word "Image" followed by a string of numbers and ending in ".pdf."
About an hour later Yahoo Groups appropriately rejected a posting from spoofer. The subject was the same except that the string of numbers was different.
I am still thinking the individual e-mails are only going to the moderators/owner, not to members, but I did set up a short-term poll.
As long as the attempted posts are rejected by Yahoo, they should not appear in the digests.
FOOTNOTE: On December 2, 2015 we had the most number of rejected attempted posts for at least the past 12 months. (Usually its less than a handful if any) I checked a site yesterday that tracks cyber attacks and interestingly enough on November 30, 2015 and December 1, 2015, the site reports some massive attempts at Denial of Service attacks in multiple countries. I have no idea if these were connected, but I wondered about it.
Steve