How long will messages stay in Queue, and how to change it?

How many days will a failed message stay in the Postfix queue, until it is automatically deleted?

And how do I configure this setting?

Thanks.

maximal_queue_lifetime (default: 5 days)
http://www.postfix.org/TUNING_README.html

Hello,

i sent email from my server but all mail landing in mail queue. Please let me know what the issue is there.

I found this error in message-

036CA9E0922    41878 Sat Apr 30 00:57:53  mail@bestwebit.com
(Host or domain name not found. Name service error for name=bourkestreetbakery.com.au type=MX: Host not found, try again)
                                         info@bourkestreetbakery.com.au

please let me know how can i solve this problem.

may be temporary error at "bourkestreetbakery.com.au"
is another queue give same error?