Hello,
this is Semi-OT but since a lot of people run Postfix before Exchange I
hope to find some knowledge here. Also heads-up :-)
We have a couple of Exchange customers behind our frontend MX servers.
We don't turn them up until they have configured their HBT servers to
reject unknown recipients and we have verified SMTP callout to them.
One customer is migrating from Exchange 2007 to Exchange 2013 and it
seems to be impossible there. There is some documentation about
"Recipient filtering" here:
http://technet.microsoft.com/en-us/library/jj218660%28v=exchg.150%29.aspx
But it does not work. Until we realized that Exchange started rejecting
the recipients, but in DATA stage.
mail from: <t...@test.de>
250 2.1.0 Sender OK
rcpt to: <doesnotex...@test.customer.de>
250 2.1.5 Recipient OK
data
354 Start mail input; end with <CRLF>.<CRLF>
test
.
550 5.1.1 User unknown
This gets even worse when the mail has two recipients ... doesnotexist@
does not exist, t1@ does...
mail from: <t...@test.de>
250 2.1.0 Sender OK
rcpt to: <doesnotex...@test.customer.de>
250 2.1.5 Recipient OK
rcpt to: <t...@test.customer.de>
250 2.1.5 Recipient OK
data
354 Start mail input; end with <CRLF>.<CRLF>
test
.
550 5.1.1 User unknown
mail from: <t...@test.de>
250 2.1.0 Sender OK
rcpt to: <t...@test.customer.de>
250 2.1.5 Recipient OK
data
354 Start mail input; end with <CRLF>.<CRLF>
test
.
250 2.6.0 <MSGID> [InternalId=2740189134859] Queued mail for delivery
This is not only unusable for Recipient validation, but will reject
legitimate mail since you cannot reject individual recipients in DATA
with SMTP.
According to this threat:
http://social.technet.microsoft.com/Forums/en-US/exchangesvrdeploy/thread/91c26fd2-aa0c-4006-9326-ece609bf4f67/
this is expected. I can hardly believe that.
We do not have in-house experience with 2013 yet. Can anyone shed some
light at this?
Verification against AD (LDAP) would be an option but requires a lot
more configuration and coordination with the customer, and some of them
are uncomfortable opening those ports anyway.
Bernhard
