Which customer segment should I use to target non-marketing text messages like alerts and announcements?

Colligso strongly advises you (see TCPA) to use default segment selected by Text campaigns for marketing related messaging from your business. This segment of customers have explicitly chosen to follow your business by opting in.

However, there are cases where you want to alert/inform your customers about your business due to some emergency. For example, one of the businesses using Colligso Textin wanted to inform its customers about temporary closure due to COVID-19. Such a message would be appreciated by customers. It was not a marketing message. In such cases you can use a segment prefixed with keyword deliveredUsers.