Hi,

I have received some useless spam messages and the conversation says "This conversation contains automated system messages sent to you by Speedrun.com."

I don't find a delete button for these messages. Also, I don't find a button to turn these messages off. What do?

The message isn't really spam or useless, it's an automated message from the site advertising their new challenge.

You currently can't disable it or delete it, so just click on the message to mark it as read and ignore it. These messages don't get sent often.