Maybe this...

Code:
$= SetOption("WrapOnEol","On")

$cmail = CreateObject("CDONTS.NewMail")
If @error = 0  
     $cmail.To = "xyz@@mycompany.com"
     $cmail.From = @userid+"@@mycompany.com"
     $cmail.Subject = "Client Problem: "+@wksta  
     $cmail.Body = @wksta+@crlf+@userid+@crlf+@fullname 
     $cmail.Send
     $cmail = 0
EndIf


You doubled the @'s in the TO field but you forgot to in the FROM field.