I am having a problem in Outlook. When I receive some e-mail, and I try to reply, this is what I get....

Try using another Email program to see if the problem is related to Outlook or your ISP.

You can get some good ones here -> http://www.tucows.com/mail95_default.html

I used Eudura and it works fine. I prefer Outlook though....called my ISP and they said it was my problem not theirs. It is real sporatic, sometimes I can forward, sometimes I cannot.

Which Outlook is it?

Is the problem as simple as you are typing in the address wrong? Or that persons email has been shut down? I am in charge of a list serve at school here with about 40 people on it and every once in a while I will get an email like that saying that either the persons inbox is FULL or that address is no longer existant. That could be the same problem....

No, all I do is hit "Reply" and type my message then hit send, then imediately I get that message.

Have you tried the "detect and repair" option in outlook XP - its under the Help menu.