Stop mail from bouncing

[david at thekramers.net (David Kramer)]

Josh ChaitinPollak wrote:
> 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

in main,cf:

# The unknown_local_recipient_reject_code specifies the SMTP server
# response code when a recipient domain matches $mydestination or
# $inet_interfaces, while $local_recipient_maps is non-empty and the
# recipient address or address local-part is not found.
#
# The default setting is 550 (reject mail) but it is safer to start
# with 450 (try again later) until you are certain that your
# local_recipient_maps settings are OK.
#
#unknown_local_recipient_reject_code = 550
unknown_local_recipient_reject_code = 450