Migration Plan Exchange 2003 to 2007 Hub, CAS, Mailbox Roles

We are planning on migrating from 2003 to 2007.  
We are wondering about the HUB transport role.  Our 2003 server is currently acting as a mailbox, CAS and hub transport for all of our mail.

When we migrated a few mailboxes to the new 2007 server, new mail weren't being delivered to the mailbox, regardless of the CAS and our clients connectivity.  The actual email from inside or outside wasn't being delivered to the migrated mailbox.
Is the 2003 Exchange server not capable of the hub transport role to the new 2007 mailboxes?

As we decide upon our migration design, we need to know whether we have to put a 2007 hub transport role in place?
We are already thinking of putting a dedicated 2007 CAS server in place, and then migrating our mailboxes to a separate 2007 server with CAS and mailbox roles in place, but what about the HUB transport?
When and where do we move the SMTP mail that is being published to our 2003 server to one of the two 2007 servers, and which one should be the hub transport?
peter_ophovenAsked:
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AkhaterConnect With a Mentor Commented:
What if I have a 2003 exchange server with mailboxes and, and I have a 2007 box with CAS and mailboxes, with the hub transport role on it, will it deliver email to the 2003 mailboxes while in coexistance?

No


Alternatively, we are thinking about having two separate namespaces, the 2003 exhcange server be webmail.company.com and the 2007 exchange server would be mailbox.company.com.  We are thinking about doing this as a way to stagger our migration from the 2003 mail server to the 2007.
You can do that but I wouldn't


 But we are worried that if our 2007 hub, cas, mailbox server was the primary hub transport for the company, that mail would still be delivered to the 2003 mailboxes while in transition.
Yes it would still deliver to 2003


Akhater you implied that while we transferred mailboxes from the 2003 to the 2007 we needed a 2007 server with the CAS role only, and we couldn't have mailboxes on it.
yes you will need a cas only 2k7 server during the migration if you want to have a unified name


So, we are now thinking of deploying a temporary 2007 CAS server, while we transfer mailboxes from 2003 to the 2007 CAS / Mailbox / Hub transport server that we already have in place.
Yep


Although, I am not sure if the temporary 2007 CAS server would have the HUB role or not?
Yes it can

And, I am totally confused about which servers need Certificates?

your cas servers
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Alan CoxSr. Systems EngineerCommented:
You have to have a CAS and HT in every AD site that has 2007/2010 mailbox role.
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AkhaterCommented:
>Is the 2003 Exchange server not capable of the hub transport role to the new 2007 mailboxes?

No to deliver mails to a 2007 mailbox you will need a 2007 HUB and to access a 2007 mailbox using https/outlook anywhere you will need  a 2007 cas

>We are already thinking of putting a dedicated 2007 CAS server in place, and then migrating our mailboxes to a separate 2007 server with CAS and mailbox roles in place,

what is the purpose of that ? how many users are we talking about ? any clustering plans ?

>but what about the HUB transport?

HUB can coexist happily with the CAS, Mailbox or both

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peter_ophovenAuthor Commented:
What if I have a 2003 exchange server with mailboxes and, and I have a 2007 box with CAS and mailboxes, with the hub transport role on it, will it deliver email to the 2003 mailboxes while in coexistance?

Alternatively, we are thinking about having two separate namespaces, the 2003 exhcange server be webmail.company.com and the 2007 exchange server would be mailbox.company.com.  We are thinking about doing this as a way to stagger our migration from the 2003 mail server to the 2007.  But we are worried that if our 2007 hub, cas, mailbox server was the primary hub transport for the company, that mail would still be delivered to the 2003 mailboxes while in transition.

I think plan A is the better one, but it requires we add a second exchange 2007 CAS box during the migration.
We weren't planning for the addtional 2007 box while we have mailboxes on the 2003 server.
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peter_ophovenAuthor Commented:
Akhater you implied that while we transferred mailboxes from the 2003 to the 2007 we needed a 2007 server with the CAS role only, and we couldn't have mailboxes on it.

So, we are now thinking of deploying a temporary 2007 CAS server, while we transfer mailboxes from 2003 to the 2007 CAS / Mailbox / Hub transport server that we already have in place.

Although, I am not sure if the temporary 2007 CAS server would have the HUB role or not?
And, I am totally confused about which servers need Certificates?
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JHCompVerdeCommented:
This is SO helpful!  We are in a similar situation, and your answers (Akhater) have really helped clarify things for us.  Thank you!
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peter_ophovenAuthor Commented:
Thanks.  We are moving forward and am excited about the design.
PJO
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