It’s automatic over Windows 2k/XP. Not with 9x/Me.
I don’t use Eudora. But it’s not supposed to use 127.0.0.1 etc. with any other email client anymore.
The configuration in some email clients, specially if you used different configuration due to spam killers, does not come back to the original values correctly. You have to do it manually and set the email client like you will if avast! does not exist.