RE: RES: RE: Multiple SMTP relay servers - Pos sible Solution?

  • From: Chris Wall <Chris.Wall@xxxxxxxxxxxxxxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 21 Jul 2004 16:06:21 -0400

I plan on using one of the GFI relay servers as a primary (all services
running such as whitelisting, Bayesian, DNS Lookup, Virus Scanning, Keyword
and Attachment blocks, etc...) the other server will only be configured to
use keyword blocks, attachment blocks and virus scanning.  This is only for
failover purposes so the secondary does not have to be as restrictive.  I
look at it this way - it is better to have too much e-mail coming into the
organization than none at all, as long as it is being scanned for virus',
attachment types and some keywords.  
So far, for my overall solution I have this:
Set the internal Exchange servers (with IMS running) to use internal DNS to
deliver mail to the weighted MX records pointing to GFI SMTP Virtual Servers
in the DMZ.  Then the GFI SMTP Virtual Servers will reference external DNS
for final external mail delivery....
Now I have to find a way for internal mail to have redundancy.  Using IIS 6
or 5 on the SMTP Virtual Servers in the DMZ, I need to find a way to have
them deliver to either of the internal Exchange servers in case the primary
IMS is not available on one of the Exchange servers.  I have received
several responses telling me to have the SMTP Virtual Servers deliver mail
using DNS.  I can not do this as the SMTP Virtual Servers are pointing to an
external DNS server.  Can I set Smart Hosts on the SMTP Virtual Servers to
send mail to two IP address in IIS?  If not, I have a single point of
failure for mail coming into my organization if the Smart Host fails...
If I can specify two IP's in the IIS Smart Host field for my domain (for
example [;] )  would this work?  Or is this not
possible in IIS?
Very confused now and I cant find anything that states I can set 2 IP's in
the IIS Smart Host field.


From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx] 
Sent: Wednesday, July 21, 2004 3:47 PM
To: [ExchangeList]
Subject: [exchangelist] RE: RES: RE: Multiple SMTP relay servers

Hi Tiago,
Good point! One location I worked with had 4 relays! One for MailEssentials,
one for MailSecurity, One for iHateSpam and one for SpamAssisin. All inbound
mail was run through all four relays before hitting the corporate Exchange
Servers. Turned out to work pretty good and very few false positives and
very little spam got it.
I'll need to write up the configuration some day at
<> .
Get the book!
Tom and Deb Shinder's Configuring ISA Server 2004
MVP -- ISA Firewalls

-----Original Message-----
From: Tiago de Aviz [mailto:Tiago@xxxxxxxxxxxxxxx] 
Sent: Wednesday, July 21, 2004 1:23 PM
To: [ExchangeList]
Subject: [exchangelist] RES: RE: Multiple SMTP relay servers

Also, be careful that if both relays run GFI MailEssentials, your spam
database on the SMTP gateways won't be the same (mail that is whitelisted on
one server may be considered spam on another).


Tiago de Aviz


(41) 340-2363 <> 


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