There are times when a message should be delivered to a subset of list members. For instance, you might only want to deliver your message to contacts that live in a certain location or use a specific product of yours. Criteria are used to select a subset of list members, and are based on the same search options as found in the Search Contacts page. These predefined searches are saved and used within the mailing process.

The Mailing Criteria page

In the example above, this criteria would limit the recipients of a mailing to those contacts that have an email address that contains 1to1service.com.