Messaging residents
Conversations that belong to the property rather than to a phone.
A resident can start a conversation with the people who manage their building, and only with them. There are no group chats with neighbours and no personal mobile numbers handed out.
The thread belongs to the organisation. When staff change, the next person opens the same history rather than starting from nothing.
Telling everybody at once
That is a broadcast, not a conversation, and it is a separate thing. Write once and send to everyone or to a single property. Drafts and sent are kept strictly apart so a half-written notice cannot go out.