There are three big mistakes that can lead to a waste in time and money when you send bulk email.
The length of the message can hinder a bulk email campaign drastically. The longer a message the more spam keys can be found in your email. More often, the recipient will not read a long message. Think about yourself receiving an email that you didn't expect. Are you going to read it if it is longer than one paragraph? Probably not. If the recipient wants to learn more, they will click through the email. They are not looking to learn all the information in the email.
The general rule of thumb in advertising is that it takes at least 3 impressions to get an action out of the audience. It is the same with mass email software. The emails must be sent out at least 3 times to the same recipients throughout the course of a month. It is also good to follow up the emails to really make the best use of the list. Whether this means calling the recipient or sending follow up emails.
A misleading subject line will cause a reader to immediately delete an email upon opening it. Although, this may get a customer to read it or click through from time to time, it is not a good practice. It is deceiving and will cause immediate deletions of your email. Opens are great; however, the real goal is to get click throughs to generate traffic on the website being advertised.