I'm hoping someone can help me with the following query.
I have a concern regarding changing the MX records on the external DNS servers to prepare for the exchange 2013 migration in coexistence environment which has exchange 2007 on windows 2003 R2 servers 64 bit.
We currently have exchange 2007 environment which is setup with an external DNS MX record of e.g. mail.contoso.com and mail.blogs.com both of which currently point to same external IP address e.g. 184.108.40.206. Both domains are registered to the company I work for. This is how it was setup when I first joined the company.
My concern is, would there be any mail flow issues, if I was to setup exchange in coexistence environment and configure exchange 2013 environment to use mail.blogs.com and point it to a different external IP address i.e. 220.127.116.11 (using exchange 2013 edge transport server in DMZ to send and receive emails) whilst leaving the exchange 2007 to use mail.contos.com pointing to the existing IP 18.104.22.168 (using client access and hub transport roles and not the exchange 2013 edge transport server). Our default SMTP email address is email@example.com.
Both domains contoso.com and blogs.com have been setup as accepted domains on exchange 2007.