Start New Conversation with Reply
You're writing back and forth on a single "conversation" with a large number of unrelated friends. Then you decide to write a new message to all of them about a new subject. You COULD compose a new message, and manually insert each of their names in the To: / CC: fields. (This group of friends are not on any "list" because it just wouldn't make sense to create a list for these particular persons.) There should be a quicker way. Why not be able to simply hit "Reply all", then change the subject line, and delete all previous messages in that old conversation (CTRL-A, Delete), and begin composing your new message? If you try that option today, all your recipients will see the former messages even though you deleted them and changed the subject line! Why?? If you delete all the older messages and change the subject line, it ought to be EQUIVALENT to composing a new message. But currently, it doesn't work that way. Why not?