REVISED:Exchange 5.5 IMS routing problem

The users are not part of any local network that the exchange servers are on. Email comes into my mail server to their mailbox with an address of user@mydomain.com and is forwarded to a custom recipient with the address user@sub.mydomain.com. My primary exchange server is set to deliver mail for sub.mydomain.com using DNS. It is at this point that it sends it, for some reason, to another exchange server on my WAN and has it deliver the mail.

Each custom recipient was created on the primary server. They do not list a home server, only a home site. The Home "Server" for each user is also the primary server. Each user's NT account, for their real mailboxes is also created on the primary server. I have their mail forwarding to the Custom Recipient only.
I have one Exchange organization, and one Exchange site. The two servers are in this same site. Both have the IMS installed.

Steve,

I thought I needed to ask more questions, but now I believe I may have an answer for you.

I will make the assumption that all your "MX" records are correct making this a real Microsoft Exchange issue having nothing related to IP name services.

You may simply need to modify the "cost" value in the "site addressing | routing" section in the secondary or sub.mydomain.com server. Change that to a number higher than the one that is in your primary. 100 is the worst route and 1 isthe default and best route. Make sure the primary cost is 1 and the secondary cost is more.

The MTA handles routing of messages and you actually only need one IMC for each site. If you have 2 servers in the same site you need to let microsoft MTA know how to handle the routing of those internet messages.

John Burchell
Network Manager
Green Mountain Energy Company

John:
I have the IMS's at each location because they both have their own Internet connection, but the WAN connection between them is low speed.
I understand what you are saying about the routing cost. I really don't want a work around. I want a fix.
I have nothing configured that is telling the IMS on the primary server to deliver mail for this subdomain using anything but itself. This is why I don't understand why it's sending the mail to another IMS to be delivered. Why isn't it doing the delivery?

Excuse me, I really don't have enough information afterall. I'm sure I can help you solve your problem if you wish to contact me offline.

If you have one Exchange organisation and one site, but that site has two exchange servers, one being the primary server, then it may be that the other server is being used by the main server as a bridgehead. If so, bridgehead servers do deliver mail. It may be that the other server on the wan is closer to the recipient of the message which gets routed there.

Questions:
1. How long has this been occurring? From the initial setup of Exchange? From a point where you created the custom recipients? From a change on the IMC properties? From the moment you created a sub-domain?

2. Does this happen with every message sent to the custom recipient? Or only randomly as it would if you have enabled "forward to host" set on the IMC Connector Tab of Properties? An entry for forwarding to host would cause the first message to go to the primary EX server and the next message to go to the other server, the next goes to the primary and so on...

I assume you have message tracking enabled in order to follow these messages from the primary to the other EXCH server.

3. Are both IMCs receiving mail for the same domain? One is not for domain and other for sub.domain, right?

There are a couple more questions to get a better picture:

1. How are you connecting to the Internet and are your LAN IP addresses also your Internet IP addresses?

2. Do you maintain your own DNS or is it handled by your ISP?

3. Are you trying to make the primary Exchange server deliver directly to the forwarded mailbox? If so, where do the forwarded mailboxes reside?

The problem as I see it:

The two exchange servers are both in DNS as MX hosts one being under the primary domain and the other the secondary domain. The IP addresses for the servrs is the same for either Internet or WAN. With the use of the Custom SMTP Recipient containers you are actually doing the following routing of the mail.

1. The message comes in under the primary domain.
2. It gets forwarded to the custom recipient which uses an SMTP address for another domain.
3. The IMS does a lookup for the secondary domain and gets the IP address for the second Exchange server.
4. Noting that IP address actually coinsides with the IP addressing used accross the WAN it takes the most direct route and contacts the secondary IMS through the WAN link.
5. Now talking IMS to IMS the transfer of the message is made to the secondary server where the local MTA takes over and delivers the message to the mailbox.

The real question is then: How do you really want the forwarded message routed and delivered?

Looking forward to your reply...

Steve,

If I understood you correctly you want each of your server deliver Internet mail using its own IMS (not the other server IMS) . I would suggest you have to reconfigure Address Space of IMS on both servers. There is an entry like "SMTP * 1"(where * means all addresses and 1 means routing cost). However, by both have "Organization" restriction by default. I believe your problem will be solved if you change that restriction to "Location".
Or, you may want to add an entry specifically for that subdomain with "Location" restriction at both servers.

Sorry, I have no sufficient test environment to check/test that myself :-))

Hope this gives you some ideas,
Dima

The above answer is the right direction but would restrict your users to only sending out the server their mailbox resides on. This is no problem if your mailboxes are distributed between the servers but the information you have given here indicatesall the mailboxes reside on the primary server (kind of makes the secondary server worthless if the WAN link croaks). By using the location restriction the outgoing SMTP would never go through the secondary IMS. Some information for setting up Location restrictions can be found in MS KB article Q234639.

If you are only forwarding to one outbound location then you can set up routing for that domain by placing it in the Address Space for the IMS and giving it a 1 and the all others (*) route a2 on the primary indicating the primary IMS.

Do the same for the secondary IMS except for indicating itself for the all others (*) entry.

Hope this helps...

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