I made the cutover (changed the MX records) so that our mailflow will now come from Office 365 and not the in house server. The issue is Once the cutover was made. Everything worked (OWA, reconfigured mobile devices and tablet and even outlook clients out of the network).
The issue is configuring the outlook client in network. This is not my first migration. So I know that I have to change the DNS of each individual user PC to a public DNS like 220.127.116.11 so that when I reconfigure outlook it picks up the office365 setup before the in house exchange.
That part worked. The issue is once I revert the DNS on the PC back to the internal DNS the user PC's start asking for the user name and password and the pop shows that the asking server is the internal OWA link.
I called Microsoft Office 365 team and this is what they said
"As discussed over the call last week, we found that we are able to configure Outlook in External Network and the issue is only in Internal Network. We can access Outlook Web Access in internal Network which means that the Office365 Exchange is working fine. Your Local DNS Manager seems to be blocking the Query to connect the Global Server.
The problem is with the network as you have as the Local DNS is not allowing us to connect to the Office365 exchange server.
As I am not a Network Engineer, would suggest you to contact the Network Admin. He will be able to bypass the Query and connect to the Office365 Exchange Server in internal Network."
I do not have much experience with the DNS. Can someone help me with this? I need to cutover to 365 and turn off the exchange server.