I have recently installed a server with Microsoft Exchange 2013 alongside our existing Exchange 2007 server as a first step in migration. We have a single site, single AD, and just these 2 Exchange servers. I believe I have followed all the Microsoft instructions for setting this up. I have not yet migrated any mailboxes across.
To test it out I have created a new user with a mailbox on the 2013 server. From this, I can send email to the Internet successfully, but I cannot send email to a mailbox on the 2007 server. I see no error message in Outlook, it appears to have sent it but it does not arrive.
It does work the other way round - i.e. From the user / mailbox on the 2007 server, I can send email successfully to the user with the 2013 mailbox.
I can't see how to troubleshoot sending mail between the exchange servers. Please can you suggest where I can look?