have had no luck with AVG or Spamfighter with this problem,i can only receive
emails.i submit a question to the two above named companys on ther site but
cant reply via there response,i keep getting undelivered mail response.below
is an example of what i get(i have others)...

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.
The e-mail server has responded with the following error:

sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
Your e-mail message is being returned to you in the next part of this
message. Try to send the message again.

Should you need assistance, please contact your administrator or your
Internet service provider.

You can also verify e-mail client's settings, for instance:
- whether your SMTP autentization has been configured
- whether you have provided correct SMTP server name
- whether the sender's address responds to the used SMTP server domain