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

  • From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 21 Jul 2004 16:02:38 -0500

Hi Tiago,
What I would do (and what I have done before) is use a split DNS and then allow 
the relay to forward to internal Exchange Servers based on the MX records. If 
the top listed MX is not available, it goes to the second. And because I was so 
very wise :-) to implement the split DNS, the MX records resolve to the 
internal addresses of the Exchange Servers. Works a treat, and its a more 
elegant solution than smart hosts (although I quite willing to take the cowards 
way out [smart host] when the org snafu'd and used a .local domain :-))
Tom <> 
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 3:24 PM
        To: [ExchangeList]
        Subject: [exchangelist] RES: RE: RES: RE: Multiple SMTP relay servers - 
Pos sible Solution?

        (Just thinking loud)


        Point the IIS smart host to a DNS name and use round robin?


        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 17:06
        Para: [ExchangeList]
        Assunto: [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.



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