1-an public certificate with required domain name.
2-submit Microsoft MSN connect request to firstname.lastname@example.org.
Get a confirmed Mail. like:
Agreement Number: xxxxxxxx
Organization Name: xxxxxx
Access Edge Service FQDN
Your provisioning request for Office Communications Server public IM connectivity has been successfully completed. You should now be able to connect to the public IM connectivity providers for IM federation. If you have any questions or concerns about your new public IM connectivity service, or if you wish to stop the service, please contact us at email@example.com.
Note: Your provisioning request was submitted by the Microsoft operation team, on behalf of your Administrator.
Thank you for using Office Communications Server public IM connectivity service.
1 Microsoft Way
Redmond, WA 98052
Microsoft Office Communications Server
3-config ocs edge
4-config ocs pool
5-config ocs user
6-change OCS edge to public network. keep in mind that OCS edge server have to connect with MSN server via 5061 port (both side).