No-mailbox "super" Admin accounts (Ver 1.x ++)

Currently the design of Stalw.art requires Mailbox accounts in the “main”/non-tenant domain, who can be assigned administrator profiles.

I do have the cases where I’d prefer to have all the mail-receiving/sending accounts inside tenants, but I still now need a mailbox account with a domain that can be given the “administrator” profile that is outside the tenants.
This do create the contradictions where I need two accounts for myself, one inside the tenant that receives the emails for all the accounts I’m part of, and then a separate MAILBOX account (but that I don’t/shouldn’t receive/send emails from) to to only administer Stalw.art.

This then asks for the addition of a “mailbox-less” type domain that is only used for administration of the stalwart server cluster but not an actual mailbox carrying account.