"Error sending message" with Act! 2000

[Pleasants]

I installed Act! 2000 version 5.0 with W98 on a P III. I used the "internet mail" option to set up with my established dial up account. The "Check internet connection" passed. When I clicked "send" on an email, "Sending Message" was announced. At the bottom of the Act! window the smpt address was shown then "Error sending message." The "Sending Message" placard would not close.

I would appreciate any help in getting the email function working.