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

  • From: "Tiago de Aviz" <Tiago@xxxxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 21 Jul 2004 18:31:23 -0300

Well, i guess the correct would be: your IIS uses its own DNS server, put a 
secondary zone of your internal domain, and set it to forward to external DNS's 
in the DNS Server properties.


Tiago de Aviz


(41) 340-2363 <> 


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De: Chris Wall [mailto:Chris.Wall@xxxxxxxxxxxxxxxxxxx] 
Enviada em: quarta-feira, 21 de julho de 2004 17:47
Para: [ExchangeList]
Assunto: [exchangelist] RE: RES: RE: Multiple SMTP relay servers - Pos sible 

One last stupid question -- 


In IIS, since the server is set to use an external DNS server, should I just 
type in the FQDN of the internal DNS server or its IP in []'s where it asks for 
the Smart Host information?   I assume that I can not simply select the 'Use 
DNS' radio button.


Sorry to be so stupid on this, but I am confused on how to get the IIS to point 
back into the internal DNS since it is setup to reference the External DNS 
server in the TCP/IP settings of the NIC.  


Enough hand holding...  Time to experiment in the lab I guess.  Thanks for all 
of the info and suggestions.  I will be open to any other suggestions though :)



From: Lara, Greg [mailto:GLara@xxxxxxx] 
Sent: Wednesday, July 21, 2004 4:16 PM
To: [ExchangeList]
Subject: [exchangelist] RE: RES: RE: Multiple SMTP relay servers - Pos sible 

Chris, you don't need to point your relay to both IMCs, you get get the same 
effect you want by using round-robin entries in DNS. Create two host entries 
with the same name, each one pointing to a different Exchange server. The DNS 
server will return alternate IP addresses with each query. Then, point your 
SMTP relay to that hostname.

Greg Lara
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        From: Chris Wall [mailto:Chris.Wall@xxxxxxxxxxxxxxxxxxx] 
        Sent: Wednesday, July 21, 2004 4:06 PM
        To: [ExchangeList]
        Subject: [exchangelist] RE: RES: RE: Multiple SMTP relay servers - Pos 
sible Solution?

        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



        Tom <> 
        Get the book!
        Tom and Deb Shinder's Configuring ISA Server 2004 <> 
        MVP -- ISA Firewalls

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