try this:
edit the newreply temaplate, search for:
Code:
<input type="hidden" name="s" value="{vb:raw session.sessionhash}" />
and add the following immediately above
Code:
<input type="hidden" name="emailupdate" value="<vb:if condition="$emailchecked[0]!=''">0<vb:elseif condition="$emailchecked[1]!=''" />1<vb:elseif condition="$emailchecked[2]!=''" />2<vb:elseif condition="$emailchecked[3]!=''" />3<vb:else />9999</vb:if>">