There are 2 methods to change the port numbers: (Depends on the version you have)

Option 1

Eudora uses an initialization file called Eudora.ini and is normally located in the same folder as the Eudora application itself. It contains all the information needed to configure the behavior of Eudora.

Note: First make a backup of this file before making any changes to it.

Also, use notepad to make changes to the file.

The Eudora.ini file has a number of sections. Each section starts with a word in square brackets. The most important section is the one called [settings] and is usually the first section in the file.

Here you should see SMTPPort, POPPort and IMAPPort. You can change the port numbers here.

[Settings]

AlwaysConnected=0

DontShowUpdates=1

POPAccount=your acount

RealName=your name

ReturnAddress=your e-mail address

CheckForMailEvery=10

SavePassword=1

LeaveMailOnServer=0

SMTPPort=25

POPPort=110

Option 2

Exit Eudora. Look in the Eudora directory for the folder "Extrastuff". In this folder there is a file named esoteric.epi. Drag this file into the main Eudora directory. Restart Eudora then go to the Tools menu, Options, Ports, and change the ports here as needed.