In practice, you will find that you need to use an email service to assure compliance with the anti-spam laws as well as being able to conveniently sending hundreds of emails with a single OK click. If you've never tried to do so, you will find that your normal email provider will not allow that. ConstantContact is the most well known service, but I recommend small businesses start with MailChimp, because the latter is free for lists with less than 2000 email addresses. These services all provide easy-to-use templates to produce good-looking and effective emails.
The overwhelming benefit of emails as a marketing tool is the specific feedback that they provide regarding the interests of your customers. These services provide you reports with specific information regarding precisely who clicked on which link contained in each email. This uniquely enables you to tailor feedback tied to those interests. For example, you might subsequently offer a 20% discount on a red dress, but only to those who you know are already interested because they'd clicked on a link previously, thus avoiding the need to expose yourself to such a discount for your entire customer base.