Or maybe putting the POP server name in the e-mail account slot, as shown here, will do it ... hmmmm.
Hope I didn't erase Claris e-mailer. (I probably did.) But you can get it here.
How to make an aging Macintosh work in the world of 21st-century computing, with a focus on a 12-year-old Powerbook 1400cs and a 5-year-old 14-inch iBook G4