Several recent list messages have resulted, each, in a flurry of auto-rejected mail bounced back to the admins. What these messages have in common is that they contain very little text, with basically only a single web link as the body of the message... and that makes them look like spam to the (many, over-aggressive, and not-too-clever) anti-spam filters out there.
This means that in each case, some good fraction of the list population failed to see the message at all - it was simply rejected by other members' ISPs, and never delivered to some unknowable number of people. So: to maximize your chances of your mail getting delivered to people, please consider writing actual commentary about the link you're passing on. Say something about what you found interesting about it, how you're going to use it, or what it will mean to you, etc., etc. It will make the message look less like random spam, and be more likely to be delivered - and, as a side-effect, your message might itself be inherently interesting, too! Everybody wins! Put another way: mailing lists are not Twitter, they are not Facebook, and they are not text messaging; they're a medium where you are *encouraged* to write actual words, in actual sentences, that say something meaningful (perhaps whole paragraphs-ful!) about the list topic. Go forth and compose email... about folding. Or, well, maybe go forth and fold, and then write to tell us about it! Anne for the list admin gang (who are getting really tired of the spam-war fallout) P.S. This idea of writing actual content holds for "me too!" or "cool!' reply posts. Do refrain from those, too. They work elsewhere, they're silly on email discussion lists.