I like that fact that we receive emails when a trade is initiated, but is there any way to get notifications for messages posted in trades as well? I am not always very consistent about checking the site every day and have had trades cancelled because I did not respond quickly to messages posted in the trade.

Hello. This is indeed a small oversight from our side. We will implement a periodic mailer that notifies you of messages if you have not seen them in 24 hours or so.