Helm includes support for both aliases and a domain catchall.
Helm allows an unlimited number of aliases (e.g. firstname.lastname@example.org)
When enabled, the domain catchall ensures that any emails sent to your domain (@example-domain.net) will be delivered to the admin email account. This does not include emails sent to other users on your Helm. For example, if your admin email is "email@example.com" and someone tries emailing "firstname.lastname@example.org," the catchall would deliver that email to your account.
To enable this, go to Settings > Email > Catchall.