Sametime Gateway - Yahoo community is not working

I have a Sametime Gateway(8.5). My GTalk & AOL communities works properly.However, the Yahoo community does not start.

Port 5061 and 53 are open.

This is the message I receive in the SystemOut.log.

[3/31/10 19:26:06:093 GMT+05:30] 0000002a SIPKeepAliveT W com.ibm.rtc.gateway.nativesip.SIPKeepAliveThread handleComConnections CLFRC0311W: Received SIP error code 503 (Service Unavailable) while attempting to send initial invite to external community “Yahoo” at port 5061 with transport tls. Ensure the external community is configured and listening on port 5061 for scheme “sip” SIP TLS traffic

getExtCommunity CLFRC0010E: Community is not found

Thanks

Subject: same error

only against gmail (gtalk).