Based on postfix official manual,
bounce_queue_lifetime
Consider a bounce message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached the bounce_queue_lifetime limit. By default, this limit is the same as for regular mail.
Consider a message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached the maximal_queue_lifetime limit.
Since I got warning as:postfix/qmgr[10221]: warning: bounce_queue_lifetime is larger than maximal_queue_lifetime - adjusting bounce_queue_lifetime
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I want to know what's the difference between bounce_queue_lifetime & maximal_queue_lifetime
I found another explanation http://www.postfix.org/TUNING_README.html
maximal_queue_lifetime
(default: 5 days) How long a message stays in the queue before it is sent back as undeliverable. Specify 0 for mail that should be returned immediately after the first unsuccessful delivery attempt.bounce_queue_lifetime
(default: 5 days, available with Postfix version 2.1 and later) How long a MAILER-DAEMON message stays in the queue before it is considered undeliverable. Specify 0 for mail that should be tried only once.