select concat(a.username, '@', d.domain) source, a.destination
    from virtualalias a
    inner join virtualdomain d on d.enabled = 1 and d.id = a.domain
    where coalesce(a.destination, '') <> ''
      and a.action not in ('reject', 'discard')
      and not exists (
        select 1 from virtualuser u
        where u.enabled = 1 and u.alias = a.id
      )
    union all
    select concat(r.mailbox, '@', dr.domain), r.destination
    from rfc2142 r
    cross join virtualdomain dr
    where dr.enabled = 1
    and not exists (
        select 1
        from virtualalias ar
        where coalesce(ar.destination, '') <> ''
        and ar.action not in ('reject', 'discard')
        and ar.domain = dr.id
        and ar.username = r.mailbox
    )