Hope this isn’t too late to help – here’s what you do:
Edit the Autochimp plugin (plugins, edit, select autochimp)
search for “subject” and you will see this line
$options['subject'] = $post->post_title;
change it to
$options['subject'] = "Today's blog: " . $post->post_title;
Or whatever you want it to say before the post title (in the ” “).
