perldoc -U /path/postgrey
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       Auto-whitelisting clients

       With the option --auto-whitelist-clients a client IP
       address will be automatically whitelisted if the following
       conditions are met:

       �   At least 5 successfull attempts of delivering a mail
           (after greylisting was done). That number can be
           changed by specifying a number after the --auto-
           whitelist-clients argument. Only one attempt per hour
           counts.

       �   The client was last seen before --max-age days (35 per
           default).
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