High volume email software is a great way to advertise and is used by big corporations to not-for-profit organizations. There are some things to look out for, however.
The heading you choose to use for your Email advertisements could be flagged for spam if it resembles spam messages too closely. Some examples of this would be using various characters, having writing in all caps, etc. Fortunately, Velocity's html message creator and editor has spam assassin built into it. When you create a header, it will automatically rate your message by a number score. The higher the number, the more likely it is that your message will be mistaken for spam. This ensures that your campaign will be taken seriously and not disregarded.