If, whenever you try to send email from a program on your computer like Outlook or Eudora, it takes a long time to authenticate and then fails, then most likely your attempt to relay has been blocked by your Internet Service Provider (dialup modem, DSL, cable, broadband).

More and more ISPs (MSN, Earthlink, Verizon, NetZero, Mindspring, Flashnet, MediaOne, AT&T, AT&T Broadband (ATTBI), Bell Sympatico, etc) do not allow their customers to use outgoing mailservers (smtp servers) other than their own, and enforce that by blocking their customers from accessing any remote servers on smtp Port 25:

Hotmail spam filters block outgoing e-mail
MSN filter sparks subscriber ire
Verizon's Anti-competition Email Policy

The solution to this problem is to contact your ISP and ask them what Outgoing Mailserver (SMTP )  they want you to put in your mail program settings.

Another possible cause is that you have a personal firewall running on your computer like Norton Anti-Virus, Black Ice Defender, or Zone Alarm that is not allowing this type of activity. The solution in that case is to either turn off that software, or configure it to allow you to relay mail.

If you still having problem in sending email then contact support.