Ok, I checked; the message was dropped because it was bigger than our size limit. We limit inbound message size for a variety of reasons; one is historically attachment heavy archives consume a lot of resources and - statistically speaking - are much more likely to be spammy. (There were some horrific abuse cases involving YahooGroups around the turn of the century).
Unfortunately your message was collateral damage, which I regret and apologize for. In addition the FAQ entry is poorly worded and misleading, so I will update it. http://www.mail-archive.com/faq.html#attachments Bottom line - mystery solved but problem still exists. I am not inclined to open up floodgates on attachments or large mails for the archiving service at this point, but am willing to listen to feedback.
