Hi there,

If we have a scenario:

Mailbox A and Mailbox B 

On Exchange forwarding is configured to forward from A to B.

Question: If an email is sent to both mailboxes with both smtp addresses in the to field, would that email arrive in Mailbox B's inbox once or twice? Does Exchange detect that it's arriving twice and only allow it to arrive once?

Many thanks for any help in advance

Will arrive only once, if the mailboxes are in the same organization. If one mailbox is located say in Outlook.com and the other one in EO, it will arrive twice.

• Marked as answer by K Alaho 5 minutes ago

Ah, thanks for your help! 

I also found this http://blogs.technet.com/b/exchange/archive/2004/07/14/183132.aspx 

Case closed!