If you mail out an 'eflyer' simply as an image attachment, a lot of email programs will not display it by default for security and anti-spam reasons.
A much better way of doing email mailouts is to actually create it as a standards compliant HTML document that will gracefully degrade (ie, if the program refuses to display images or any advanced styling, it would still display to core message as basic text). It would also link to a copy of the email as a page on your website with a link to click 'if the email doesn't display properly'.