Suggestions for interforest communication 1

[unclerico]

I have two forests which contain 1 domain each, forest a (domain a) and forest b (domain b). Both are Windows 2000 Native DFL and both are Exchange 2000 Mixed mode. I will be migrating the domain and exchange information in domain b to domain a. Before I perform the migration I have been asked to provide all of the users in domain b an e-mail address from domain a (adding domainA.com as a recipient policy and making it the default). My question is if the MX record pointing to domain b is mail.domainB.com and e-mail is sent from a user in domain b as user@domainA.com and the recipients mail server is set up to do reverse lookups will this fail? Is there any way to set it up so that all e-mail when generated in domain b will get sent to my exchange server in domain a and then relayed out to the internet from there? If so, how will incoming mail work? I hope I am clear. Thanks for your help.

 

[RichardHuang]

In your scenario, outgoing emails are from Domaina or domainb, but all show as domaina. Incoming emails all go to domaina server, and some of them will forward to domainB, depending on who are recipients. I think this will work without any problem. Reverse DNS lookup will not fail because it checks if your IP is registered but not necessarily exactly match your domain. In addition, you can update your reverse DNS records for domainB ip, and it doesn't affect regular DNS query.

 

[unclerico]

ahhh, I see. Thank you for clearing that up...star for you.

 

[unclerico]

Here's what I'm thinking:
1) On domainB, create a recipient policy for domainA.com
2) On domainB, create an SMTP connector and set the smart host address to my domainA Exchange server
3) In domainA I have user accounts pre-created with forwarding set to their domainB account
4) Exchange on domainA will then take care of all incoming and outgoing e-mails

Does this sound like it will work?

 

[RichardHuang]

2) for outgoing emails, domainB doesn't necessarily forward to domainA first. But you can do so if you want.
3) You don't need to configure each individual account to do forwarding. Check this KB:

http://support.microsoft.com/kb/321721

 

[unclerico]

Ok, now I'm confused and I apologize for it as I am not even close to the level I want to be at with Exchange so please bear with me.

Domain A has a recipient policy with domainA.com as the default and domain B has a recipient policy with domainB.com as the default. Now, I add a new recipient policy to domain B to match that of domain A, domainA.com and set it as it's default. If I decide to do an SMTP connector with a smart host pointing to my Exchange server in domain A I can see how the e-mail will be sent with no problem. My concern is how the e-mail will be received. When my Exchange server on domain A receives an e-mail destined for someone that actually resides in domain B but has a domain A e-mail address, how will Exchange get the message to them? My understanding is that Exchange will look the recipient up in AD and in this case the recipient won't actually exist in domain A's AD so it will get NDR'd. When I read the link you provided it sounds like if Exchange can't find the account in its AD it will forward the message via the SMTP connector that was configured in the article.

As for the SMTP connector I was talking about a few posts back, I told the other engineer where I work about this and he insists that if e-mail is sent for domainA.com through domainB.com to the internet, when a reverse lookup is done the message would get rejected. By doing this we risk being blacklisted. Can you shed some more light on the reverse lookup issue?

I hope I am not confusing you or making this way too complicated. I REALLY appreciate you taking the time to help.

 

[RichardHuang]

1) When domainA gets some emails that not in AD, it will forwards those emails to DomainB through SMTP connector. So receiving part should work fine;
2) To adress the concern for reverse DNS lookup for DomainB, you can call DomainB's ISP (or whoever it gets IP from), ask them to update the reverse DNS record, adding domainA name in, then evetything should be okay.