Each time an item is bought you have listed in CS you get an email to let you know.

Would encourage players to log on more regularly too- especially new players with only a few seller slots.

For those with hundreds, why not have the ability to disable email alerts (they are probably always online) or tailor emails; for example one email a day or one email a week.

Not sure if this can be done for unregistered accounts, but it's def an incentive to get registered then!

If email alerts are possible maybe tailor options including guild invites, friend requests, items expired in CS, and more!