No sender's email address in a message posted to the group?

We don't allow anonymous posting..but somebody got through with (no subject) and (no author).. Portions of header are below..

How can I prevent this from happening again?

Bill

Comment: DomainKeys? See http://antispam.yahoo.com/domainkeys

DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=lima; d=yahoogroups.com;

b=E1CGoU2OfhQgpkRfMUsVM9alViWcXerdbFA...

Received: from [66.218.69.2] by n32.bullet.scd.yahoo.com with NNFMP; 16 Mar 2007 13:25:29 -0000

Received: from [66.218.66.158] by t2.bullet.scd.yahoo.com with NNFMP; 16 Mar 2007 13:25:29 -0000

X-Yahoo-Newman-Id: 12999105-d782

MIME-Version: 1.0

Message-ID: %26lt;1174051529.860.76747.m18@yahoogroups.co...

Mailing-List: list prospectcommunity@yahoogroups.com;

No sender's email address in a message posted to the group?network

turn ur spam guard on it wont let anything without a complete header in unless u changed ur setting 2 allow a certain address

%26 u can go 2 ur internet options %26 add the address 2 ur don't allow list 2 make sure it doesn't happen again %26 even though they never do anything about anything u can try abuse@yahoo.com they'r suppose 2 catch

that

No sender's email address in a message posted to the group?norton

report it or block it