First step would be to try this out on the latest release, we have done some work on this issue, 1.4.18 is a bit old.

On Jul 14, 2016, at 4:19 AM, Miroslav Levanic <Miroslav.Levanic@enghouse.com> wrote:

Hi, 
I’m using FS 1.4.18. I’m using TLS and SRTP. I’m trying to initiate outbound call with destination set to sips:something using "originate {return_ring_ready=true}<destination> &park xml default” command.
Checking outgoing trace, I can see that destination in INVITE SIP Request URI becomes sip:something. Is there a way to force or enable ‘sips’ instead of ‘sip’?  
 
Regards,
Miro