Cross thread

[hidoa]

I have posted this in two places....I apologize in advance.
The first time I posted it in the General Forums under Operating Systems. As I looked at the other threads, none have replies, so at least hopefully I'll get a reply this time, even if it is for getting negged...

Once again...

Okay, here is the dilemna

I am running Windows 2003 Server Web Edition.
I am sending all mail to a smarthost in the DMZ.

I know there is the option to send without using the smarthost, but that is not possible with the network setup. We are not allowing outbound email to public network, only to dmz smarthost.

My question, How do I obtain redundancy? Can I specify two smarthosts in the smarthost box separated by a comma. Or can I put a DNS name in the smarthost box and then put 2 DNS A records into the host file and it will do round robin? Or does the smarthost dns lookup only do A records or does it actually lookup MX records for the DNS name specified in the smarthost box, in which I could put two mx records for the smarthost specified...

Any ideas??
Thanks in advance..

[mohaughn]

Yes you can put multiple IP addresses-

http://support.microsoft.com/default...b;en-us;257426

You can also put in multiple FQDN's, or 1 FQDN and have DNS roundrobin through A records. Or use a combination of FQDN and Ip addresses. The article covers all of it.

You have to use brackets [] with a ; to seperate IP's. I would use IPs instead of FQDN's.

FQDN's need to be translated through DNS, so you could have a DNS problem that could cause mail delivery issues.

If you are in an environment where your IP addresses change a lot using DNS could have its benefits but in my particular environment we use IP addresses because our smart hosts never change addresses. Or atleast change very rarely so changing the IP address is not a big deal. You just have to remember to change the smarthost settings if the IP of the smarthost does change.


**CORRECTION- When you specify the FQDN in the smarthost and tell it to use DNS it will always look for an MX record associated with that FQDN first. If there is no MX record it will look for an A record for the FQDN. So as long as their is an A record that correspsonds to the FQDN it will find the right host. I guess you could say that this is a longer DNS search, but in reality it isn't. If you have an MX record defined it will have to retrieve the A record associated with the MX record anyways, so the same amount of data is returned to the mail server. This wasn't documented at the MS site because it is part of the RFC for SMTP and DNS.

[hidoa]

Mohaugn, Thank you, you have answered my question.
And I did google forever for it!

[dinowuff]

mohaughn

On your question about DNS. I would have to guess that the smarthost option is using DNS A records. It already knows that it is a mail system because you have specifically told it to use that host, so it doesn't need to do a mail exchange lookup. I can't find this documented, but I'm pretty sure that is the case.

I think you must specify a MX record. Too lazy to search. But if you do find the doc's please post the link

Thanks,

Dino

[mohaughn]

Originally posted here by dinowuff
mohaughn



I think you must specify a MX record. Too lazy to search. But if you do find the doc's please post the link

Thanks,

Dino

Yeah.. check my correction out. You guys posted before I got my original post edited... It is looking for an MX first, and then will search for an A record.


Bottom line- you should us MX records.



Here is another MS article that details how to configure both the sending server and the relay.

http://support.microsoft.com/?kbid=293800

Mohaugn, Thank you, you have answered my question.
And I did google forever for it!

support.microsoft.com is your friend. Of course when I googled for SMTP smarthost IP, and the MS article for Exchange2003 was the second one listed..