reject messages with quotation marks in the local part (SMTP)

Hi,
I've got a issue because of my server has been added to a relay black list
(http://www.dsbl.org).
I use Windows 2000 Server SP4 SMTP service.
They say that my mailer is accepting mail for relay because it accepts
messages with the RCPT TO specially formatted:
RCPT TO:<"name1@theirdomain.com"@mydomain.com>
the recipient address contains two @ symbols and the first one is enclosed
between quotation marks. I've verified that, effectively the Windows 2000
SMTP server accept these specially formatted messages...

Is there any way to reject completely any message that uses quotation marks
in the RCPT field???

Thanks

--
Alberto Borja.