Below is an example of what is known as "phishing" which is an attempt to aquire your username, password or other information. Don't be fooled by these emails.
De : System Administrator [mailto:email@example.com]
Envoyé : Friday, February 24, 2012 04:39 AM
Objet : Your mailbox
Your mailbox has exceeded the storage limit which is 5GB as set by your administrator, you are currently running on 10.9GB,you may not be able to send or receive new mail until you re-validate your mailbox. To re-validate your mailbox please send the following details below:
If you fail to re-validate your mailbox, your mailbox will be De-activated!!!
System Administrator »