Changing "forward all mail through this connector to the following smart hosts" automatically

Posted on 2007-03-26
Last Modified: 2012-08-13
Hello all,

Our Exchange Server, part of SBS 2003 Premium, is connected to our cable provider. This provider forces us to send all outgoing messages to one of their "relay" servers, so our SmallBusiness SMTP connector "forward all mail through this connector to the following smart hosts". That’s not a problem.

Now we are setting a DUAL WAN PORT firewall and we need the most automatic way to change that in case that the cable connection goes down. In other word, we wonder if there is a programmatic way of changing that value to send messages out thorough the other internet connection.

Thanks in advance.
Question by:phermi
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LVL 104

Expert Comment

ID: 18794105
The most you can do is load balance it. So have both ISPs listed. If one of them requires authentication then you will have to use two SMTP connectors with the cost the same.

The other trick I use is to use a third party relay host. That way it doesn't matter which connection is used, the messages are ending up on the same address.


Author Comment

ID: 18795523
Hi Simon,

Thanks for your reply. let me give some extra info and allow me to ask for clarification. With both pipes UP, the WAN 1 - Cable - relaying on provider SMTP serve will be in charge of ALL traffic but VoIP, which will go on the WAN 2. I do not want to do load balancing between the WAN port in order to guarantee the best possible voice quality; but if the WAN 1 Cable is down, al traffic is picked up by WAN 2.

In the incoming mail I have no issues because two MX records exist, one per each connection, 10 for WAN 1 - Cable and 100 for WAN2.

On the outgoing, are you suggesting me to create another SMTP Connector with a higher cost that the one that send all mail to my provider's SMTP? If so, will this work when the WAN 1 is down .. meaning will Exchange send the traffic via the "costly" one that is up?


LVL 104

Expert Comment

ID: 18795684
Exchange isn't as clever as that.
If you have two connectors with address space set as 10 and 100, then the connector with the cost of 100 will never be used. Exchange will try to use the lowest cost connector that matches its requirements and if that doesn't work it will queue the messages.

To give you another example, if I was setting up a connector to route all email via the smart host and then another connector to route email for AOL via another smart host then I would setup the SMTP Connector for AOL with a cost of 1 and the connector for everything else as a cost of at least 2.

If you want to use two smart hosts then you either have to put them on the same connector separated by a semi-colon (;) or setup two connectors with the same cost.

Now I haven't actually tried this... but I am told that if one doesn't work in that scenario, it should try the other one on the next try cycle because the cost is the same. I don't have dual connections to test with.

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Author Comment

ID: 18796421
Sorry if I confused you, but 10 and 100 are for my MX records; the connector have 1 for the Default SmallBusiness Connector and 10 for the Backup.

Despite this info,, that reads:
"On connectors with an identical address space, costs work the same way as they do on routing group connectors. For example, you create two SMTP connectors to the Internet, Connector1 and Connector2, and each has the address space of *. Because Connector1 has better network connectivity, you always want to use this connector (unless it becomes unavailable) to send mail to the Internet, and you give Connector1 a cost of 1. Then, you give Connector2 a cost of 2. As long as Connector1 is operating correctly, Exchange always sends messages through that connector because it has the lowest cost. If Connector1 becomes unavailable, Exchange uses the connector with the next lowest cost, Connector2."; I can confirm that waht happens is exactly what you described. With the internet connection down for the first connector, the messages were just queued; never passed onto the second connector with no smart-host defined.

I do not have a second smart host to use, so I hope there is a way to have some kind of failover for message delivery.



Author Comment

ID: 18796504
btw, where is this information being stored? I mean the contents of "forward all mail through this connector to the following smart hosts" ...
LVL 104

Accepted Solution

Sembee earned 500 total points
ID: 18796517
If you are bringing in a second internet connection then that ISP will have an smart host that you can use. I have yet to find an ISP who doesn't, unless you are connecting to a back bone in a data centre somewhere.
The other option - as I outlined earlier is to use an external host - independent of your ISP. If you have your web site hosted elsewhere, then the web host might have a service that you can use - or you can purchase a mail relay or mail hop service - these are scattered all over the internet - or just pick up some cheap web hosting that includes email.

LVL 104

Expert Comment

ID: 18796521
I have no idea where the information is being stored, probably in the domain somewhere as it is an org wide setting, not a server side setting.


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