Exchange Organisation Relationship with 2 Partners

Question

Hey!

I have
Exchange Server A: mail.a.com
Exchange Server B: mail.b.com
Exchange Server C: mail.c.com

All exchange server run in different AD Domains and have autodiscover etc. configured.

Every exchange server has a unique secondary smtp address a.com, b.com, c.om, BUT
all primary smtp addresses are company.com. There is a mailgateway in front where the MX of company.com points to. The gateway has a list with every user from every exchange organization and transports the mail accordinly.

Here's the problem:

I want to enable the possiblity of free/busy sharing between all 3 organizations.
I could create a Organization relationship between Exchange A and Exchange B and tell the connector to "roam" domain company.com, so it works between these to. If i want to add company.com to a second relationshio between A and C, Exchange says that company.com is already added to another connector.

I know thats a difficult tasks, but I hope somebody already had that problem or maybe an idea.
Major changes are unfortunalty not possible (like migrating all ADs to one or something like that) Building a ressource forest with one exchange for all is also not possible.

What I want to achive is that a user with mailaddress smith@mathieu.company .com on Exchange A can look for free/busy information for user example@mathieu.company .com which could lay on Exchange A, B or C.

Any ideas?
Thank you
CS

Answer 1

Have you read the guidance about sharing calendar between two orgs?

How did you tell the connector to roam company.com? By modifying "Source server" of the connector? I don't understand what's the relationship between this connector setting and your requirement.