Old messages and safety.

I don't have access to the old users I sent messages to. They aren't my friends and I'm no longer in their server. I want to be able to talk again or at least find my messages from those other users I messaged that are no longer in my DMs and aren't in my server so that I can delete any private information just in case I may have forgotten to delete before closing the DM.

Another note, can we also have a clear messages on servers we are no longer in? Any mention, anything from me. Anything that links it back to me.