The virtual voicemail app documented by @Phong Vu has a few issues:
DELIVERY_MODE_ADDRESS env var is required.
Whitepages API endpoint is no longer available.
Just wanted to document these for his tracking purposes.
Using the RingCentral Phone for Desktop, you can dial or receive test calls, send and receive test SMS or Fax messages in your sandbox environment.
Download RingCentral Phone for Desktop:
Tip: switch to the "sandbox mode" before logging in the app:
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