Exchange 2010 Edge Server Mail relay from Site A to Site B

In our exchange 2010 setup we have 2 sites and an edge server at each site with separate internet connections.

What is the best method to get Site A to send mail through Site B edge server if Site A edge server goes down and vice versa please?

We have HUB/CAS at both sites and MAIL Servers.

I am able to see the edge servers from both sets of HUB/CAS servers, I have also done an edge subscription to both edge servers site related and cross site fine with the correct ports open etc.

But when I switch off the Edge server at Site A it cannot send main to Site B edge.

edge servers have the default smtp receive and send connectors only.

Do I need to set others up to achieve this?

Just trying to find out where I am going wrong.

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XCONBLRConnect With a Mentor Commented:
Well, in Exchange 2010, there is no way that the mails can automatically failover to other site. There needs to be manual intervention of disabling the send connectors to achieve this.
The reason behind this is because of removal of something called as link state information from the servers.
now, you can achieve this using a different mechanism.
Where you do not configure the edge servers for edgesync and use them like relay servers and manually create send connectors for mails going out to internet to point to both edge servers as smart host. When you do this, if one of the edge server goes down, it will use the other server.
Another very important point that you have to remember is that edge server should be allowing relay for mails coming in from the hub servers. (IP based relay restrictions should be provided)
Downsides of this approach :
1. No edge sync possible
2. The mails will be sent to both the edge servers all the time in round robin as both are in the same send connector .
Good things about this:
1. You can achieve automatic failover even in 2010 as the Send connector has 2 smart hosts and in case one does not respond, server sends it to other smart host.
SeanSystem EngineerCommented:
Have you added both edge servers to the cas's send connector?
Colchester_InstituteAuthor Commented:
Is that route mail through smart connector?
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SeanSystem EngineerCommented:
Yes that would be the setting with an edge transport server
Colchester_InstituteAuthor Commented:
Going on what you have mentioned there, can I keep the Sync at the sites with edge then add a 2nd send connector to the edges aswell?

OR can i sync the 2 edge servers at both sites to Site A, then in a DR scenario manually change over to site B if required?
SeanSystem EngineerCommented:
I don't think there is a way to do a fail over situation (don't quote me on that im not 100% sure) but i think the only way is to either have them balance by using a single send connector with both edge servers in there. i think it uses the first available for its load balancing so i would think most of your traffic will still go to the local server anyways.
Both are possible. Syncing with both the Edge Servers with one AD site is definitely possible. Creating send connectors manually is also possible.
But yeah, in case of a failure of a smarthost on the connector (provided there are no multiple smarthosts), it always will be manual actions to make the mails flow again.
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