Sorry if I’m wrong on this, since I only played with Eudora’s personas (personae?) once, back when I signed up with a second ISP when it looked like my “old reliable” might be teetering on the edge of going under. (I’m using Eudora 6 by the way, but I think the following is also true for several versions back.)
Obviously if you don’t set up any more personas, then all you’ve got is the “dominant” (“default” would have made more sense to me, but then who am I?
), with its tools/ options settings.
But if I remember correctly, each additional persona gets a more or less complete, and independent, set of options to itself. So it’s a fairly close cousin to having multiple users in Windows itself.