Although, flash can be included in your newsletters it is not recommended as not all email clients support flash content. As an example, Microsoft Outlook, the most popular email client in the world does not support flash. A better way to include flash content is to link to your web based flash application from within your email. You can also send flash content as an attachment to your email, however, the flash animation will not automatically play. Also, keep in mind many businesses block such attachments.