I think what we are looking are two different things here. Jeff is saying that you can use TinyContent to display links, whereas I think you are wanting to create a content area or block that opens webmail live in that content area/block.
I think the best way to do this is with a custom menu. Go have a look for a xoops module that allows you to create a custom menu block. I can't remember than name of the module, but I know it's there. You should then be able to turn the custom menu block on, then define menu items for this block. Create a menu item that is simply a link.
Greg