Each post that you immediately publish will be added to your blog as the most recent post. Your email notifications follow your RSS feed, which displays the 10 most recent posts by default (just like your blog homepage). So, if you have a post you would like to add without sending an email notification, you will need to add it as an older post by back-dating it to show a published on date earlier than that of your 10th most recent post.
This will prevent the post from being sent to email subscribers, BUT will also not display the post on the homepage of the blog.
If you have non-blog post content, you can also add a new page. New pages do not trigger an email notification.