Question about "guaranteed delivery"

["meaculpa" <meaculpa () punkass com>]

Hi all,

probably will be a long story, but pls, if you know of a product that could
do this, pls let me (and the list) know.

Currently we have a three-layered network, separated by firewalls
(FW-DMW-FW-BE-FW-Internal). All networks are also divided in VLAN's. In the
DMZ we have multiple SMTP servers to send/receive mail from the
Internet/Other agencies/Private networks). ALL messages go to the BE network
for decryption and content scanning. When content is considered safe, the
message will be forwarded to other systems in the BE of Internal network and
then processes by either scripts, e-mail clients or production processes.
For outbould mail we use several Exchange servers that forward the SMTP
messages to the content scanning devices. As you can imagine chanes of
failures are big, they happen and e-mails and/or data gets lost.

I was thinking. It must be possible to place a box in the DMZ that receives
ALL SMTP messages inbound, does content scanning/decryption, sends the
message to the same kind of box in the BE, checks if the message came
through and then delivers the message to the endpoint. The checks as
decryption/content scanning can be offloaded to other boxes if needed. I
know there are proxy server out there (Blue Coat amongst others) that can do
this with HTTP and the content scanning gets offloaded to other boxes via
some sort of plugin solution.

What we need in short is some sort of black box/software solution/method to
receive e-mail and be able to guarantee the delivery to our own boxes on the
DMZ, BE and Internal networks. For outbound messages we need to be able to
guarantee that the outbound message got sent away. Wether it reaches it's
endpoint is of no real concern since that could be solved with S/MIME (I
think). Of course we need to be able to know what messages did not got
delivered, why if possible and some sort of method to reprocess the message
or do some sort of manual delivery.

Thank you for any and all answers.

Mea


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