> >HI.

> >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

> I would think using a SMTP gateway for all the outbound mail is the
> best solution.