Computer Issue: Entourage

We have a desktop iMac and I write on a Powerbook G4. I use Entourage as my e-mail application, and the mail from North Park just shows up (like magic to me) at home in my Entourage account. But, today suddenly I started getting a -23012 error message, something with not making connection, and I can’t get the phone folks to figure it out. I called Apple, Microsoft, Comcast (our server?) — no closer to a resolution. My brain works like this: I’ve got internet service, so I’m online. But, I can’t get the Entourage on more than one computer in the house to connect for accessing or sending mail. Any ideas?