If mail module is installed and enabled in eBox, and you wish to create one mail account to a user, it must be done going into Users and editing our desired user, where you can also set an alias for the user mail address. Check User accounts to know more about the eBox user configuration.

To set an alias to user groups, you have to get the group configuration page using Groups . If mail module is enabled, an alias can be set for all group members. Check User groups to know how to get to group configuration.