We have people sending email just internally and its being detected as spam. Here are the headers:

Yes, score=4.44 tagged_above=-10 required=4 tests=[BAYES_50=0.8, DOS_OUTLOOK_TO_MX=2.845, HELO_NO_DOMAIN=0.001, HTML_MESSAGE=0.001, RDNS_NONE=0.793] autolearn=no

We just upgraded to zimbra 6.0.7. What is this DOS_OUTLOOK_TO_MX ?

Any help would be appreciated.