As well as the suggestion to allow the messages to be addressed to oneself so that you have somewhere in game to keep notes I would like to suggest a second type of note for use by those who like the role-playing and getting into character
The Captains Log/Blog - the idea is an area where a running log can be created which is published to all players after a predetermined delay which I suggest is set to somewhere between 7 and 10 days.
@eDave. Another one for you. You can now send a message to nobody. (Simply don’t add any recipients)
It will then appear in your inbox and you can comment on this message to keep your log.
edit: Actually Dustin Morgan has been asking me for this feature since day one of the beta so its especially for him too. (Not sure if he is still playing. )