What this means is that after your mailbox reaches or exceeds 15 Megabytes of mail on the server, additional messages will not be delivered to your mailbox. Also, there will be a soft quota limit of 10 Megabytes. If your mailbox drops below 10 Megabytes, the clock is reset on the soft quota. For the vast majority of users, the quota system will be completely invisible. A vanity e-mail address serves as a pointer to the original mailbox.
Any mail sent to the vanity address ends up in the original mailbox.
A vanity alias can be created by using the Account Management section of the MindSpring Homepage.