The Lync client will likely throw the following error message "The server is temporarily unavailable. If the problem continues, please contact your support team"
If you look at the SIP traces you should see this something similar to the following:
Text: The source domain of the remote user client's message is not in the list of internally supported domains
Result-Code: 0xc3e93d72 SIPPROXY_E_EPROUTING_MSG_CLIENT_DOMAIN_NOT_INTERNALSIP-Start-Line: REGISTER sip:sipdomain.comSIP/2.0
In Lync 2010 we do add a new SIP domain and could be provisioned and enabled in the time it took for CMS replication to occur. In Lync 2013scenario is very different whenever we add new SIP domain, we have to have restart Edge server Access service before log in using the new SIP domain.