Runbox supports a so-called “catch all” function for email hosting. This means that you will receive mail on any valid address for your domain without having to setup an explicit alias. All mail will automatically be received by your runbox account.
Use this function with care. You will receive mail on every valid address for this domain name. Some spammers run so-called dictionary attacks, which means that they send to spam to many common names within a given domain. You will receive spam on all these addresses, so make sure that you have your spam filter activated.