Hi grasscarpet, What do you mean by "from a software program"? Are you using Thunderbird? What do you mean by "through Mozilla"? Mail does not go through Mozilla. The message indicates that a server at an e-mail service provider rejected the message because it seemed to be spam. I cannot tell from the information provided if the server was your provider's outgoing server or the intended recipient's provider's incoming server. In any case, this problem does not have to do with Thunderbird. You may want to do some research to learn about the characteristics of e-mail messages that are detected as spam so you can avoid them.