There is an option in SpamX to configure it to NOT send a complaint to an email address that contains any part of the string that you add to the SpamX do not send list. You can add items to your own do not send list by clicking the 'Configure' button, and adding the domains/items that you want SpamX to look at before sending.

For example, some of the items in my list are:

IANA.ORG
NIC.MIL
NE.JP
COM.AR
NET.BR
NIC.BR
TIP.NET
ARIN.NET
RIPE.NET
VALUEWEB.NET
NET.CO
COM.MX
COM.BR
COM.PL
COM.HK
COM.TW
NET.MX
NET.IL

This example would prevent SpamX from sending a complaint to ABUSE@IANA.ORG, ABUSE@NIC.MIL,...., etc....