Exchange Hybrid to Exchange Online - AD Sync enabled

[__AlexXx__]

Hi All,

I have a scenario with two redudants exchanges 2019 onprem and Office 365.

All mailboxes are hosted in cloud and we are using no smtp in onprem server.

Is there a known process to proceed with decomm of onprem server? Does the Microsoft cover this process?

Just did some researches and AD Sync could be a issue to proceed with this migration.

Thanks in advance

[#2 · Accepted solution]

Hi,

Since all your mailboxes are already in the cloud (Office 365), you don't need your on-premises Exchange servers anymore.

If you're using Azure AD Sync (which synchronizes your on-premises Active Directory with Azure Active Directory), you might need to keep one Exchange server on-premises. This is because Azure AD Sync uses the on-premises Exchange server to manage some things.

Make sure all your emails are flowing through Office 365 and not through your on-premises Exchange servers. You can get rid of most of your on-premises Exchange servers, but... If you need to keep Azure AD Sync, you should keep one Exchange server on-premises. This will help with management and resource conservation.

Thanks

[#3]

Just for others that could be looking to the same scenario,
We can demote the last Exchange Server, keeping a vm only with EMT to manage the users using powershell.

Source: https://learn.microsoft.com/en-us/exchange/manage-hybrid-exchange-recipients-with-management-tools