Many Internet access ISPs now block port 25. To access an outbound server other than your access ISPs, you can set the SMTP port to 587 if your email hosting ISP supports the official email submission port 587. Most email software makes it fairly easy to change the port - Eudora is a bit quirky or shall we say, esoteric.

Shut down Eudora if it is running.

Find the folder where Eudora is installed, such as c:\Program Files\Eudora

Look for a folder called something like "otherstuff" and enter that folder

Find the file called "esoteric.epi"

Copy that file to the \Eudora folder.

Now run Eudora.

Under Tools, Options, you should now have a new option called "Ports"

Change the SMTP outbound port from 25 to 587 and save.