<header>Hosts/domains to hand off mail to on invalid destination </header>

<center><tt>fallback_relay</tt></center>
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This parameter specifies zero or more hosts or domains to hand off mail to if a
message destination is not found, or if a destination is unreachable.

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By default, mail is bounced when a destination is not found, and delivery is
deferred if a destination is unreachable.


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