I have a problem with 3CTX and Timico VOIP provider. The registration sometimes fails to register so the incoming calls default to our Analogue lines. The event log shows : [CM104001]: Registration at 'Timico' failed. Host 'sip:XXXXX@keme.co.uk:5060' is not available! The 3CX log shows : 11:54:19.312|.\Registrar.cpp(599)|Log2|Registrar|ClientRegs:nFailure:[CM504005]: Registration failed for: 10000@Timico; Cause: 503 Service Unavailable; warning: ; internal 11:54:19.312|.\Registrar.cpp(609)|Log2|Registrar|ClientRegs:nFailure:[CM504007]: Next attempt to register 10000@Timico is scheduled in 10 minutes This happens randomly between 20 - 40 mins all the time. I have the Registration set to 120 seconds which I know is extreme but if I set it higher then the problem is I wont know if the connection needs re-registering for an hour at the least. The other weird part is it even fails registration when there is a live call incoming. I have checked the firewall and there are no blocked packets to or from Timico on any ports including : TCP 5060 UDP 5060 UDP 9000 UDP 5090 TCP 5090 UDP 10000 to 10049 UDP 34285 Any help would be appreciated also does anyone know how to change the re-register time out from 10 mins ?