I need some confirmation on a theory we have right now about something happening in our environment.
We are currently in a transitional phase between Exchange organizations. Without getting into the whole design or the logic behind it, we have the following setup:
1) Legacy organization (Exchange 2007) has user Alice with proxy addresses:
2) New organization (Exchange 2010) also has user Alice, but in this case with proxy addresses:
The primary is set the same as on the legacy organization right now so that if the user sends mail from the new organization it will have their correct current From address.
MX records for all of the domains except example.com go to the legacy organization. The MX record for example.com goes to the new organization.
The plan (don't ask why) was to require users who want to keep mail from the old organization to forward it to the new organization using Outlook 2010's Forward function. In this example, that would mean Alice forwards a message from her legacy mailbox to "A123@example.com", and it shows up in the new organization.
However, what actually happens when Alice does that is it ends up right back in her legacy mailbox. When Outlook goes to resolve "A123@example.com", it appears to resolve to new new organization recipient. (We can see this in the Outlook properties for the recipient - the proxy address list can tell us which of the two organizations is resolving the account.) This makes sense to us. However, when the mail is sent, it appears the primary address of AJones@contoso.org in the new address book is picked up, so the final e-mail address is actually AJones@contoso.org, hence the old organization getting the message.
On top of this, we can't change the primary address on the new organization right now, so we can't test what I'm about to ask right now, but we need an understanding to move forward in other areas.
When we can change the primary address on the new organization to be A123@example.com, we think this will fix this. Is that a reasonable thought?
Also, and in some ways more important in the long term, is my basic explanation of how this is "going wrong" right now on track with how Outlook and Exchange actually do these things?