If you receive the error in your store "Email Error: The following From address failed: email@example.com", then changing the email type back to the default type of PHP instead of SMTP will usually fix the problem. Here's how.
- Log into the admin section of your site
- From the "Setup" menu, choose "Shop Setup"
- Click on "E-Mail Transport Method" and click "Edit"
- Click the circular 'PHP' button to select this option
- Click Update