Stop mail from bouncing

[josh at offthehill.org (Josh ChaitinPollak)]

Hello,

We have a problem at work where our slapd LDAP daemon has been going  
down repeatedly. When this happens, our SMTP daemon (postfix on  
another machine) starts bouncing messages because it can't look up  
and verify account names. Is there a way to configure postfix to not  
bounce, but send 'try again later' or something else, when it can't  
connect to the ldap server?

Isn't there a way postfix can tell the difference between 'no  
account' and 'account verification mechanism unavailable'?

We recently split the ldap and mail servers onto two separate boxes  
to make them more reliable, but this seems to have only caused more  
problems. Should I be mirroring the ldap config on the mail server?

Of course, stopping slapd from crashing is my first priority, but  
this hard dependancy between the two is a real problem. I know there  
is an option to configure postfix to accept mail for all addresses,  
even ones that it isn't aware of, but I'd rather not resort to that,  
then nothing will ever bounce.

-Josh