Microsoft Teams > free with SEND's O365. Chat, online meetings, integrated with Planner and other Microsoft Office products. A great way to work collaboratively online.
Use your work email address (@send.org) for SEND business and your personal email (e.g. @gmail.com) for your personal communication. Archived emails you have written as a SEND leader may be a helpful resource for the next leader in your role, and it will be much easier for that next leader to be able to access those emails if they are located on the send.org server. At the same time, you do not want to share your personal emails with the next leader. Here is a web article about the importance of using a company email address.