I am having problems with mail messages from authorized users sending to local domain, being marked as spam, when they are sending it from their homes, and their home IP's are listed as open relays.

This is how the message is tagged:

Code:
X-Spam-Status: Yes, score=7.659 tagged_above=-10 required=6.6
	tests=[ALL_TRUSTED=-1, BAYES_00=-1.9, DOS_OUTLOOK_TO_MX=2.845,
	HTML_MESSAGE=0.001, RCVD_IN_NJABL_PROXY=2.224, RCVD_IN_PBL=3.335,
	RCVD_IN_RP_RNBL=1.31, RCVD_IN_SORBS_DUL=0.001, RDNS_NONE=0.793,
	T_HELO_NO_DOMAIN=0.01, T_LONGLINE=0.01, T_MSGID_NOFQDN2=0.01,
	T_NOT_A_PERSON=-0.01, T_PUBLISHED_DNSBLS=0.01,
	T_PUBLISHED_DNSBLS_BRBL=0.01, T_THREAD_INDEX_BAD=0.01]
Since, in order to be able to send email user has to login to server first, I would like to avoid message being marked false positive. Do you have idea how to do this?