Does InDesign have “Data-driven Graphics”?
I believe InDesign might have the functionality you’re after – I looked into using its XML tools a little ways back for a pretty complex multi-page document (didn’t work out) but it may work out if you’re sticking to a fairly simple and consistent newsletter layout. Adobe has a bunch of InDesign XML tutorials as PDF’s here… Ah, guess you’d also have to munge your text file into an XML file.