If you provide client accounts at a price on your Interspire Email Marketer install then you may have use for giving potential customers a trial account on occasion. This is easiest to do by created a User Group with “trial” like permissions setup and then creating user accounts for each individual during their trail phase. If they decide to buy you can simply assign their user account to a new User Group and the transition is seemless.
You will have to play around with the user group permissions that make the most sense for you but it would make a lot of sense to prevent the user from changing SMTP options, bounce options, and to limit the number of contacts and or sends they can send. Otherwise you want the trial user to be able to use all the various functions so they can fall in love with the features.