notification mails

I have installed the guestbook 2.3.1 using cpanel and everything is working fine, but this one little problem. When I receive the 'notice mail' someone has signed my book, I open the mail and the FROM shows the email address. But when I click on reply and send the mail, I get this error in Outlook Express....

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'Bianca Quinonez'. Subject 'Re: New DD guestbook entry', Account: 'designs@', Server: 'mail.dreamworkdesigns.com', Protocol: SMTP, Server Response: '501 <Bianca Quinonez>: "@" or "." expected after "Bianca"', Port: 25, Secure(SSL): No, Server Error: 501, Error Number: 0x800CCC79

I figured out what is happening, but don't know how to fix it. It's like the NAME and EMAIL ADDRESS are switched somehow in the 'notice mail'. The OE error happens because the NAME is being replied to, not the EMAIL ADDRESS. To better describe what I mean, I've taken a screenshot which you can see here...
http://dreamworkdesigns.com/bookerror.jpg
I've blacked out part of the email address for our visitor's privacy.

I have another advanced guestbook set up with a different host and there is no problem replying to those 'notice mails'.

Hopefully someone will know what to do to fix this problem. Thanks

Deb

Jam'n? Does anyone know what I'll have to do to fix the error with the notice mails?

Deb