[Reply] Reply-all for Twitter @mentions
By default, Reply will include only the author of the tweet you're replying to (as an @mention). Sometimes though, you might want to reply-all and include all users mentioned in the tweet.
You can do this on an individual basis by clicking on the To field within the composer and then selecting the accounts you'd like to include.
You can also enable this behaviour by default, by clicking on Settings on the left hand side of your dashboard, then selecting the Account tab, and finally switching the Default to reply-all for @mentions toggle to on.