Exchange 2010/2013 co-existence and domain change

[birchanger]

We're struggling, being part of the way along the yellow brick road to Office 365. We have an O365 tenant of myschool.com, but our legacy inhouse servers were using myschool.lea.sch.uk. We want to get an Exchange 2013 server alongside or in place of our Exchange 20101 server prior to completing the move to hybrid O365, mostly because sources suggest that the wizard in the 2013 client access role helps.

 

This is where we are:

 

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• I've added our new domain to the Exchange accepted domains, so we now happily accept mail on the new domain.
  
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• I've changed the email address policy to send from the new domain.
  
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• I installed a new Exchange 2013 server, set all virtual directories to be in the new domain and installed a wildcard certificate.
  
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• I reconfigured the SCPs to use external hostnames, have set up external and split-brain internal DNS for the new domain and mucked about with outlook anywhere settings until they look sensible
  

 

 

This setup (almost) works, in that mailboxes on the 2010 server have not been broken and a test mailbox on the 2013 server works (but requires login). However a mailbox migrated from 2010 to 2013 cannot be accessed - an Outlook client generates a certificate error whilst apparently looking for the full (external) name of the 2010 server, which is odd considering that the old server need no longer be concerned with this mailbox.

 

Anyway, all of the above is background but may be relevant. To bring the new server into play I simply swung over the nat rule in our firewall, adding any necessary exclusions. Incoming traffic (mail and owa) was now routed to the new server. It all seemed to work.

 

BUT - we couldn't send to the outside world. The send connector is still sending from the old server, so naturally had lost its nat setup. As send connectors are organisation-wide settings I can find no way to force the system to send from the new server.

 

Any ideas?