If you use voip.ms and want to use their softphone on iOS with SIP over TLS, these are the settings that worked for me:
- First, enable Encrypted SIP Traffic option for the sub-account (and you should really be using sub-accounts for softphone registrations) on the voip.ms control panel.
- On your voip.ms softphone on your device, Click on Account Setup, Click on i next to the account to modify settings, click on Advanced Settings, change transport protocol to tls(sip).
- Click on Secure Calls, and turn on SDES to Required for both incoming and outgoing calls
After this, you should see your softphone registration show up as TLS on voip.ms portal and when you make/receive calls you should see the lock icon in the softphone indicating secure channel for the call.