How can I start a group conversation with multiple client users or all clients users associated with a company?

First, we recommend that you familiarize yourself with how "channels" work.

Creating a messages channel

To create a new messages channel, click on the + on the Messages page and select New conversation. Then select one or more clients, or select a company, and submit. A new channel will be created or, if the channel already exists, you will be redirected to it. Depending on the type of channel you create, it will be accessible by one or more of your clients. You can now send and receive messages in the channel.