Microsoft Lync Call does not work through SonicWall.
Place Microsoft Lync server behind firewall in NAT mode. Make Lync calls (audio/video) to external Lync users from inside the LAN network. The calls get connected, but there is no Audio or Video over the call. Microsoft Lync uses SIP over TCP. SonicWall supports SIP over UDP only in present firmware releases, hence SonicWall will not do the transformation at application layer for SIP over TCP.
Resolution or Workaround:
Workaround is to setup Microsoft Lync server to use SIP over UDP so that SonicWall can do the transformation at application layer for SIP over UDP. Or configure Microsoft Lync Server in Transparent Mode with WAN interface.
There is already an RFE filed with engineering team to have SIP over TCP support DTS# 109443.