So what you are saying is that each email sent passes a LDAP request
from the appliance to Imail. Seems like the appliance would use some
sort of caching to prevent unnecessary traffic on the network. I
will check it out.
caching LDAP/SMTP queries can be negative and/or positive.
If you don't export recips to IMGate, postfix's
recipient_address_verification will positive/negative cache SMTP
probes to the maibox server (same as with sender_address_verification).
But the vast majority of spam is to non-existent, and never-seen,
recips, so the vast majority of spam results in a probe to the
mailbox server's LDAP or SMTP service. Caching can't help.
Exporting the recip database from the mailbox server to the MX
gateway is THE BEST design to offload the spam burden from the maibox
server and MOST EFFICENT in reducing the load on the MX itself. I've
seen 800 MHz PC rejects 50K bad recips/hour with no impact on
throughput of legit recips.
And if one insists on spending $1000s on purchase and eternal annual
$subcriptions, one can greatly reduce those $1000s by putting IMGate
out front and buy/subscribe to a much less powerful machine because
IMGate will reduce the traffic to the $box by 90+%.
Len
