When you create a campaign you will be asked to select a "Type" of campaign. You have 2 options:

1. Standard 
2. Suppression

1. Standard

A standard campaign is what you would select to post in your leads from a given source for anything other than a STOP LIST (Explained in suppression). This will allow you to use all feature linked to a campaign like validation services, caps etc.

2. Suppression 

This type will ONLY be used as a home for all customers who do not wish to be contacted, other names could be STOP/OPT OUT list. You would create and link to a STANDARD campaign to ensure no-one on suppression list will be contacted.