> I had the same problem that was mentioned here before:
> http://groups.google.com/group/microsoft.public.exchange.admin/browse...

> For those who doesn't know - greylisting is used on some mail servers to
> tempfail first attempt of an email, asking the sending server to retry later.

> In short (more details will follow) - Exchange 2003 SP2 failes to re-queue
> messages sent to some servers that implement greylisting.
> This does not happen all the time (some messages go through but sometimes it
> fails).
> When the problem happens, those emails are hidden in some kind of a black
> hole, and the sender does not get an NDR nor Delay notification, even after
> those timeouts expire.
> Such messsages can remain "lost" for days or even weeks, until the SMTP or
> Information Store service is restarted.
> After a restart of SMTP service, Exchange suddenly finds those lost emails
> (I guess they were in the Mailbox Store), and retries to send them or returns
> NDR to the sender.

> I have just openned a PSS case about this and working with Microsoft.
> However this issue is not easy to re-produce, so I would like to get
> feedback from you as well.

> My questions to you -
> Have you encountered similar problems, such as users complaining that they
> got NDR for a message they sent 2 weeks before, or that the recipient calls
> them and tell them "why did I got now and email you sent a week ago?"
> (And you find out that the recipient server uses greylisting).

> Meanwhile I have found those workarounds and currently I don't have the
> problem, but it still needs further investigations:

> Workaround 1: Send emails to greylisting domains via an ISP Smart Host
> (using SMTP connector).

> Workaround 2: Use scheduled tasks to restart SMTP service every day.

> Workaround 3: Change SMTP virtual server retry timeouts (this does not seem
> to help but I changed it anyway to values you can see below).

> Here is a more detailed report that I have also sent to Microsoft PSS:

> When sending outgoing email to mail server that implement greylisting,
> sometimes Exchange retries the message later (as expected),
> but sometimes Exchange simply does not retry delivery ,
> and neither sends NDR nor Delay notification to the sender.
> Two weeks later when I restart the SMTP service for installing security
> updates (such as IMF updates),
> then Exchange tries again to send those "lost" messages.

> The problem seems sporadic - sometime it works, sometimes it doesn't, with
> the same configuration.

> The problem appears with several different destination domains. The common
> thing is that all of them use greylisting.

> Description of the server
> A single server with the following software:
> Primary roles = DC + Exchange + File server.
> Windows 2003 Standard SP1 (upgarded from win2000 about 1 year ago).
> DC + DNS + FSMO ROLES (This is the only DC in the network).
> Exchange 2003 SP2 with IMF configured and enabled.
> Symatec Corporate 10.0.2 (file protection) + SMSMSE 5.0.1.208 (mail
> protection).

> Connection to the internet:
> Cisco PIX 501 firewall ver 6.3(1)
> ADSL line to the ISP (PPPoE).
> ISP name = Bezeq International (www.bezeqint.net)

> DNS settings:
> The same server is an internal DNS server, and uses ISP servers as
> "forwarders" .

> SMTP connector settings:
> Send using DNS (the default).

> SMTP virtual server settings (related to the issue):
> Logging = NCSA common log file format.
> Delivery retry interval (I have change the defaults):
> First retry = 1 minute
> Second retry = 2 minutes
> Third retry = 15 minutes
> Subsequent retry = 30 minutes
> Delay notification = 1 hours
> Expiration timeout = 2 days

> --
> Yizhar Hurwitz
> http://yizhar.mvps.org

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