If Eudora complains that an "OT Library can't be found" and that it's going to use MacTCP instead, then the machine needs an OT stub library. Install
OpenTransportLib.68K
into the extensions folder, and run again.
Any 68K machine running an Open Transport version prior to 1.3 needs this stub library. You can check on the OT version by doing a Get Info on one of the existing OT libraries.