Why not to use your ISP or GMail for E-marketing

One of the first questions I get when setting up a CRM system - either ACT! or ZoHo CRM is "how do I mail merge?".  Below are some reasons why you should not use the email merge directly from SageACT or ZohoCRM, and the alternative you should use.  Whatever you use, PLEASE do not think you can use your ISP or GMail to send mass emails.