As of April 10, 2010, users@lists.kamailio.org and sr-users@lists.sip-router.org have been unified. Although messages can still be posted to both addresses, the one to be primary is sr-users@lists.sip-router.org. You can subscribe or change options via web at:
Now the project is offering a single place for community discussions via email related to stable versions and generic topics, ensuring access to knowledgeable people from both Kamailio (OpenSER) and SIP Express Router (SER).
With the release of version 3.0.0, you can blend extensions from Kamailio (OpenSER) and SIP Express Router (SER) in same SIP server instance, having a common public forum for emails is a natural evolution step.