postfix queue setting questions

[Tenaka]

where can I check the settings for my queues?
for example I have an undeliverable (outgoing) message sitting in my queue for more than 1 day it seems, what are the general queue mail handling settings used in the howto ? I mean when will I get the error that the mail was undeliverable?

[falko]

You could run

postconf -d

to see Postfix's default configuration values. I think Postfix tries to deliver a mail for 5 days.
Also have a look at the commands postqueue and postsuper.