BOARD18 is a tool for playing “18xx style” games via Email.
The BOARD18 game session associated with a PBEM game is used to display the game board and the stock market for the game.
It will run as a web service accessed via the player's web browser.
The How To page linked to here contains step by step instructions for setting up a PBEM 18xx game.
BOARD18 is open source software available under the MIT License
NOTE: For more information on 18xx style games, see this wikipedia article.