[exim] :defer: and retry

What sort of retry hints are recorded for a redirect router with
data=:defer:

hold_for_a_bit:
    driver = redirect
        verify = no
    condition = ${if >{$acl_m_hold_until}{$tod_epoch}}
        allow_defer= yes
        data = :defer: Holding until $acl_m_hold_until
        more = no

Is it per address, per domain, or what?

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