The Eudora mailer can exchange messages via a file system. For those users that have to use the Eudora (or other mailer of that kind) in this mode, create text mailbox files (using user names as file names) in the File InBoxes folder, and enter their names in the Alias table:
<username> = username@File
For each user, follow the instructions in the mailer application manual to specify the file username inside the File InBoxes folder as the user InBox, and specify the File OutBox as the folder where the mailer should store the messages it "sends".