Many businesses that have websites have invested in Constant Contact or Verticle Marketing or other services that cost between $40 and $200 a month to email 100 to several thousand subscibers/clients. These services are typically valuable but for those of you who are a little green when it comes to internet marketing here is a simpler solution that is more customized and cost $0 per month.
You will need:
a. an email address that supports SMTP
b. Sendblaster (which has a basic free version) or Interspire which you may be able to get through your hosting provider
c. a list of client email addresses preferably with names as well
Using Sendblaster (since there is at least one free version) compose an email that you want to send to all of your clients. How personal you want to make the email is up to you but the more personal typically the greater the response rate. You'll want to have your email addresses and corresponding names in a csv spreadsheet. Names in the first column and email addresses in the second. If it's the vice-versa that is fine, but make sure names are in one column and email addresses in the other.
You then import the list into sendblaster and select which column is the name and which is the email address. It will show you a spreadsheet with one column listed for both. Then as for typing the email you simply replace where you want the person's name shown with #NAME#. So if you are email firstname.lastname@example.org and you say #NAME#, a word from Your Company in the subject, Matt's name will be shown.
In the email body do the same:
we spoke a while back about bla bla blaisdkasd sksa dl
and #NAME#, I thought you might be interested in giving us more business.
Once this is written and saved simply plug your smtp settings into sendblaster and set the send rate for something like 40-60 emails per hour. DO NOT send them at max speed. If you have a large list you can get a smtp account just for this purpose that will allow 10,000 sends a month for about $15 a month. Which is far better than the $200+ price you would pay with a mere newsletter service like Constant Contact.
You can use HTML in your mass email and utilize all the features already available, the biggest factor is to make the emails noticeable by utilizing variable data. According to Interspire emails are opened 6X as often when their name is in the subject.
Here is a picture of where you input the smtp settings so Sendblaster knows what email service to send through