I've modified the source code of Netscape-supplied antirelay.c plugin for Netscape Messaging Server 4.15 so that it grants relaying based on whether the sender e-mail address is in the delivery domain (in addition to original recipient e-mail address and hosts-based submission control).
You can download the modified code here [1].
Usage:
Just as with the original Netscape version of the plug-in, you specify your delivery domains in antirelay.conf:
delivery:*@your.domain.comWith the original plug-in, NMS would accept all smtp transactions with "rcpt to:" matching any of these patterns. With my version, NMS also accepts smtp transactions with "mail from:" matching those patterns.
delivery:*@your.domain.com.pl
Links:
Preventing relaying in Netscape Messaging Server [2]
Netscape's original documentation: "Anti-Relaying Defenses" [3]
Links:
[1] http://olo.org.pl/static/admin/netscape_messaging/downloads
[2] http://www2.tsc.com/%7Ebobp/nms-no-relay.html
[3] http://docs.sun.com/source/816-6044-10/ubefiltr.htm#1073677