How can mail users create aliases?

[Stefanix]

Hi,

I read somewhere that the mail user is able to manage his mail aliases.
Actually I can see only the list of existing aliases which had been created by the domain admin.
Is it posssible that the mail user can create new aliases for himself?
Would be a nice feature if he is free to create a limited amount of aliases by himself, e.g. for temporary use and spam protection.

Thanks!
Stefanix