We have made the move to O365 and because of how my predecessor left things we have a couple of small sites still using our old Exchange Server. they should be off of it in a month or so and then we can shut it down for good.  I was wondering what I will need to do for that.  I was told I cant just turn it off, but what specifically will I need to do?  

Uninstall Exchange?  Remove the server from the domain?  Run something to clean up AD? 

We have made the move to O365 and because of how my predecessor left things we have a couple of small sites still using our old Exchange Server. they should be off of it in a month or so and then we can shut it down for good.  I was wondering what I will need to do for that.  I was told I cant just turn it off, but what specifically will I need to do?  

Uninstall Exchange?  Remove the server from the domain?  Run something to clean up AD? 

You will need to at a minimum uninstall Exchange from the existing server before shutting down for good.  Additionally I would recommend stopping the services for a day and then shutting the server down for a day to weed out any hooks into the old system prior to uninstalling.

Hi,

I understand you want to remove the old exchange server in a hybrid environment.

I suggest we can refer to the below article to achieve your goal:

https://technet.microsoft.com/en-us/library/dn931280(v=exchg.150).aspx  

Regards,

David