Some types of software have features such as attachment handling, a command line silent mode and multiple message editing and selection. One of the benefits of using such software is the reduction of duplication possibilities that may cause a business to send emails to the same address more than once.
Not only is such a glitch annoying but it can also email list damage a business' reputation and image of professionalism. Whether purchased from a third party or compiled in-house, the business must be careful when using bulk email. It must be certain it is compliant with the CAN SPAM Act. Many services include safeguards that avoid any problems with this aspect of bulk mailing but any company seeking to use its own list must first make sure it is familiar with the law.
Look, I understand how hard it is to find mailing lists [http://abc-mailing-lists.com] that actually work and I've spent more than my share of time and money learning how to spot the good lists, the junk lists; who has them, and even more importantly, how to get them out of their tightly gripped hands. You are obviously smart and motivated enough to want to learn more about this industry so hats off to you because researching like you are doing pays off.