Re: Recipient Filtering and Tarpitting - any tips?

It is true that rejecting emails immidiately reduces load further down the
line. If you are virus scanning all emails (I hope) and spam filtering then
you even save more.

It is also true that the delay will keep connections open longer. This is
only a problem if you receive many concurrent emails.

In general I do recommand the use of Recipient Filtering + Dir Harvesting.
However you should test this out in order to determine how well this works
in your case. You might for example settle for a shorter delay (4 or 3
seconds).

--
Alexander Zammit
WinDeveloper Software
IMF Tune - Unleash the Full Intelligent Message Filter Power
http://www.windeveloper.com/imftune/


"Phil McNeill" <philmcneill@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:uOMIdFj9HHA.1416@xxxxxxxxxxxxxxxxxxxxxxx
Thanks much for the reply.

I do not believe we have any connection issues receiving mail currently,
although the amount of directory harvest mail our server deals with is
more than half of our total inbound mail, and at times the simple
processing of that mail can slow responsiveness of the server. I was
actually hoping that one of the side-effects of enabling this would be to
improve server responsiveness (as it's no longer receiving the actual DH
messages). Is this accurate, or will the rejecting of the messages and
handling of the 5 second delay likely offset any gains we make there? I
don't want to make this thing any slower. :)

Thanks again!

Phil

"Alexander Zammit [MVP]" <alex@respond_to_group> wrote in message
news:OnJGE9i9HHA.1188@xxxxxxxxxxxxxxxxxxxxxxx

Tar Pitting will slow SMTP failure responses. Thus SMTP failure responses
will keep connections open for a longer time.
If your server is very loaded and all inbound connections are taken then
further inbound connections would not be accepted.

However if your server is coping well with the email load I don't see
this as an important issue.

More details from here:
http://www.exchangeinbox.com/articles/020/dirharvest.htm


--
Alexander Zammit
WinDeveloper Software
IMF Tune - Unleash the Full Intelligent Message Filter Power
http://www.windeveloper.com/imftune/


"Phil McNeill" <philmcneill@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:uoF8azi9HHA.2752@xxxxxxxxxxxxxxxxxxxxxxx
We use the latest version of GFI MailEssentials for SPAM filtering, and
are looking to enable Recipient Filtering and Tarpitting on the Exchange
Server to solve the current issue we have which is remote mail senders
not receiving NDRs when they mistype an email address. I've read
through:

http://support.microsoft.com/kb/823866/en-us (regarding Recipient
Filtering)

and

http://support.microsoft.com/kb/842851/en-us (regarding tarpitting)

It seems simple enough, but I was wondering if some of those here could
comment on any gotchas I might encounter. Any performance issues, or
potential for lost mail or anything like that? It seems as if we should
actually gain some performance back since we'll no longer be processing
much of the junk that our Directory Harvesting filter is dealing with
now. We have a fairly simple single server setup.

Thanks for any comments!

Exchange 2003 Enterprise SP2 on Windows Server 2003 Standard SP1










.

Relevant Pages

  • Re: No external emails
    ... three connections doesn't sound like much of a problem. ... I did look in the virtual server this morning and they were 3 connections ... point where new mail stops coming in. ... Last night at around 9:20 all the external emails were ...
    (microsoft.public.exchange.admin)
  • Re: Sarge Performance
    ... > Minimal Debian Sarge. ... > Qmail MTA configured with up to 70 incoming connections. ... > On my old Redhat systems the hardware could scan around 60.000 emails ... > changing my MX to only contain this one server. ...
    (Debian-User)
  • Re: Some emails bounced when sent to Exchange 5.5
    ... Sounds to me like you're getting slammed by spam - it's hogging your server ... > When I use perf monitor to see the connections inbound used it hovers ... > Even though I could send and receive emails (bit slow and some emails ...
    (microsoft.public.exchange.admin)
  • Re: No external emails
    ... disconnect, I found that connection in someone's Exchange blog. ... three connections doesn't sound like much of a problem. ... I did look in the virtual server this morning and they were 3 connections ... Last night at around 9:20 all the external emails were ...
    (microsoft.public.exchange.admin)
  • Re: SMTP Woes
    ... Do you host the DNS for your external domain or is this done by your ISP ... The volume of connections your getting presuming these have ... Have you made any other changes to your network, mail server, DNS ... filtering software. ...
    (microsoft.public.exchange.connectivity)