Do you still support Eudora?
Unfortunately the Eudora software is ancient - its development stopped in 2006 - and did not evolve to keep up with the technology. Port 587, TLS, etc. will all work. The only significant change in that regard is that SMTP authentication will be required.
We've heard that the latest version (7) work with out new server, but the oldest ones don't.
You could upgrade, but keep in mind that Eudora development stopped in 2006 and we can not support it anymore.
If you're having trouble with your version of Eudora, you might want to take a look at Thunderbird or some other alternative.
You can download Thunderbird (it's free), or other email clients to replace Eudora.
You may have access to Mac Mail if you're on a Mac or Outlook/Outlook Express if you are on a Windows PC.