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 :-)) HTH, Tom www.isaserver.org/shinder <http://www.isaserver.org/shinder> Get the book! Tom and Deb Shinder's Configuring ISA Server 2004 http://tinyurl.com/3xqb7 <http://tinyurl.com/3xqb7> 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? http://www.MSExchange.org/ (Just thinking loud) Point the IIS smart host to a DNS name and use round robin? Tiago de Aviz SoftSell (41) 340-2363 www.softsell.com.br <http://www.softsell.com.br/> Esta mensagem, incluindo seus anexos, tem caráter confidencial e seu conteúdo é restrito ao destinatário da mensagem. Caso você tenha recebido esta mensagem por engano, queira por favor retorná-la ao destinatário e apagá-la de seus arquivos. Qualquer uso não autorizado, replicação ou disseminação desta mensagem ou parte dela é expressamente proibido. A SoftSell não é responsável pelo conteúdo ou a veracidade desta informação. ________________________________ 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? http://www.MSExchange.org/ 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 [172.16.1.1; 172.16.1.2] ) 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.