The first blog I created with Posterous is public. You can see that blog here: http://vstevens-pi.posterous.com/
Almost from the day I created it, it started attracting subscribers. Some of these I knew but many were strangers. This is probably innocuous, but if you are concerned about the privacy of your students, and if you intend your blog solely for class use, you can make it private.
In this case anyone who wants to view it needs to provide the password you set.
Here’s what the interface looks like. You reach this screen when you CREATE a Posterous blog.
As with all my postings so far, this one has been created by composing an email and sending it to firstname.lastname@example.org. The graphic was included as an attachment in the email. The result is as you see here.
Graphics in email are placed at the TOP of the posting, but you an easily edit this and place the graphic elsewhere in the post, as I’ve done here, placing the graphic at the bottom of the post 😉