PrintsPlus,
In PrintShop Mail, you define which of the data fields are User Input fields. You can go to Window->Data Fields, choose one of the fields, and in the Properties, set it to User Input. New fields can be added by referencing them in variables, even if they're not in your database.
After that, just place those fields in variables, and use multiple variables in the same text box. This way, you will be able to enter multiple lines of information in PrintShop Mail Web, and they will appear in the text box at the right place. Enable "Remove Empty Lines" as well in the Properties of your text box to not have blank lines if no information is entered.
Hope that helps!
Regards,
Raphaël Lalonde Lefebvre