"Also send email to" pushes your posts to people that haven't circled you. Many look at this as SPAM and may block you.
This happens when you include a circle along with "Public" then check that box when you share the post.
If a large number of people block and report your profile to Google+ for spamming, you may lose your account.
I'm sending you this note as a courtesy so that you understand what is happening when you check that box.