There are basically two ways you can send out bulk email. Before we get into how you can, let's clarify a few points.
There are basically two types of bulk email sent out.
The first, which is unsolicited bulk mail, is commonly referred to as "spam". Spam is flooding Internet with many copies of same message, in an attempt to force message on people who would not otherwise choose to receive it. Most spam is commercial advertising, often for dubious products, get-rich- quick schemes, or quasi-legal services, and is genre of Scamster. The correct definition of spam is UBE, "unsolicited bulk email".
The second, which is solicited, is commonly referred to as "opt- in" email. This differs from spam in that recipients, have asked to receive email. This normally takes form of a newsletter or ezine. An important point here, is that person can easily remove their email address from list if they don't want to receive it in future.
For purposes of this discussion, let's assume we are sending our email to an "opt in" list. Forget about spamming. Most ISP's (Internet Service Providers) will cancel your account if you do so.
You can send out your email in one of two ways. Either you can maintain list of addresses on your computer, or use a List Server.
If you maintain list yourself, and send out your email using a package such as Pegasus or Eudora, you are responsible for maintaining list - both adds and drops. If you have a lot of subscribers, this can become an unmanageable task. It also ties up your computer for a period of time while you are sending them out. Using a standard modem, figure about 15 minutes per thousand addresses.
Enter List Server - here you send your message to List Server and it sends it to your list - you can then go about your business while this is being done. It also makes maintenance of your list a lot easier. You don't have to worry about adds, and more importantly drops to list, as it is done for you. If you have only a few hundred names, you can consider doing it yourself, but when your list gets larger than that, you should definitely consider using a List Server.
Now there are List Servers and there are List Servers. Many were added by ISP's as an afterthought trying to provide a full range of service for their customers. Others have dedicated servers just for this purpose. This is important as ones added as an afterthought, usually do not provide level of service desired. They give an extremely low priority to sending out email, and it can take up to 24 hours before your message is relayed - not very good for time sensitive information.