Email forwarders for large number of users

I need to understand if there is any significant risk for forwarding a large number of email accounts from one exchange server to the new accounts on another exchange server.
In short users are moving exchange servers and into a different forest. The two exchange servers are on entirely different networks so all email will forward across the internet as if they were different companies.
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No particular risks really - the only this would be to make sure both servers (and internet connections) can handle the volume of traffic.

This is a private 'transaction' between the two mailservers, and each one will be 'know' the other - the emails will likely transit through some public routers, but the Exchange server(s) should opportunistically encrypt all the traffic so nothing should be at risk.

You aren't interacting with any other parties so you won't be at risk of being flagged as a spammer.

Hope that helps,


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Mal OsborneAlpha GeekCommented:
You may have problems with the second server checking SPF, and falsly catagorising incoming email as spam. Thsi is because it will be arriving from a IP address that does not match the one it should come from.

Just make sure that whatever you have as a spam filter does not check SPF.
Sid_FAuthor Commented:
Spam goes to domain A then gets forwarded to domain B. Even though it's expected mail domain A risks getting blacklisted
How does Domain A get blacklisted?

That would only happen if Domain B chooses to do that, and if that server knows that Server A is forwarding, you would make sure it never blacklists them.

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