[samdk]

My email address is of the form [e-mail], and I got around this issue by creating an alias for sending in Gmail that's [e-mail]. As a security measure it's not perfect, but it's not something someone's just going to be able to guess.

That solves the issue for me, but not for most (less tech-savvy) people. I think what Posterous needs is the ability to require confirmation by email when a post is made by email. I get that you can do this by setting your blog to 'anyone can post', but that seems counterintuitive, and most people don't understand how easy it is to spoof emails. As long as the confirmation can be done by email, I don't think it'd be much of an inconvenience.