I'll bump this up for re-visiting. As a site owner, I receive a TON of PM's (Conversations) and many of them are just appreciative replies for my invites I send out or my auto-responder when someone new signs up. Many of which I don't really need to respond to. I would like to select all and delete all, but haven't found any tools or controls to do so. Anyone know of any?
In your conversations list you'll see a check box next to the titles, tic that box on any of them. A popup will show up, click select all. That will select all conversations on that page. About the only way of doing it currently.
In XenForo 1.5 the welcome conversations we start can be "left" by default automatically, meaning you never see them in your Inbox. It still allows the new users to reply to them, though, so you would only see that welcome message in your Inbox if a new user actually replies to it.