Sending text messages (SMS) from Outlook 2016 for Mac

There are some commercial services like Red Oxygen with a 15 day trial for testing, which works from inside Outlook.

Another commercial approach is aspsms which does Email to SMS from inside Outlook.

A possibly free solution (untested by me) might be to install Microsoft's Skype for Outlook.com. One can send an SMS from Skype, but I do not know how well this works from Outlook.