I have an Exchange 2007 environment (Edge - Hub/CAS) that I will upgrade to Exchange 2013 in the near future (on-premises). I am using the Exchange Server Deployment Assistant (https://technet.microsoft.com/en-us/exdeploy2013/Checklist?state=2419-W-AAAAAAAAQAAAAAEAAAAAAAA%7e) and checking out the various steps in the checklist. Presently, my MX record points to a cloud-based spam filter (MXGuarddog) which forwards all non-spam email to my edge server.
How will this affect the mail flow during the transition steps mentioned in the checklist, mainly the existence of legacy and new servers?
Thanks for the input!
Dave