Last weekend, I had to deal with almost 4,000 bounce messages that were sent "from" my domain. I blamed it on someone using my domain for the reply to address, but now I wonder if it wasn't a new version of spamming through MT. "Mail This Entry" used for spam – "If you are using Movable Type's "Mail This Entry" feature on your blog, you are advised to rename your mt-send-entry.cgi file, or remove the feature entirely. If you are not using the feature on your blog, you still need to either rename the script, disable it by changing the permissions, or remove it from your server altogether." Read all about it at Girlie Matters.