The device (and especially one with such old software loaded) will not be able to directly conference with MS Teams, Zoom, etc unless you have something to gateway the call. Some of what you can and can't do will depend on how you configure it, or whether you connect it to a Call Manager, the Webex Cloud, or other call services. I'd suggest you have a good read through the Admin Guide as a starting point, and then consider updating it to a more recent version of software (TC7.3.19 is from back in October 2015 - there have been many improvements and bug/security enhancements since then).
Wayne
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