Create a server tool which propagates a player in every zone. Any tells this player receives goes to a GM, or SE employee. As this player is not in the world, the only tells they will get is from BOTS cycling through the player list in each zone.

At this point, the GM or SE employee can right click their name in the chat box. They will have the option to BAN that account. A screen capture, or log of the offending RMT message will then emailed to the player showing why his account was banned.

This takes care of tells for RMT. Shouts could work similarly, except the players would have a right-click option to submit for RMT review that would then be forwarded to the GM, or SE employee.

The bot problem would still exist, albeit temporarily. With the outlets to sell the RMT transactions eradicated, there would eventually be no incentive to BOT for RMT.