Hello,

i'm kind of stuck after migrate all of my mailboxes to office 365 about what to do with my on premise Exchange 2013.

now i have the following situation :

All my mailbox have been migrated from Exchange 2013 to exchange online, my AD is Dyrsinced and all flows are going through office365.

My on premise server is turned off since about a month and everything is going well.

i don't want to keep my on premise Exchange Server like is recommended by microsoft since i can manage what i want with AD Attributes and Powershell.

so can i uninstall the on-prem exch without worries ? since this will delete some exchange attributes on my users, how my office365 mailboxes will react? what is the best thing to do?

thanks by advance for your help !

Well, You can uninstall without worries, on O365 you only have Custom attributes synced with ad object and not exchange objects so you can uninstall without any issues.

At the end of any official guide you can see the following note:

Decommissioning Exchange can have unintended consequences. Before decommissioning your on-premises Exchange organization, we recommend that you contact Microsoft Support.

Hi,

Generally, if you do not need to manage users from on-premises and there are no additional directory synchronization requirements or password synchronization, you can safely disable directory synchronization and remove Exchange from the on-premises environment.

If you plan to keep Active Directory Federation Services (AD FS) for user authentication or keep directory synchronization, we cannot fully remove the Exchange servers from the on-premises environment. However, we can decommission most of the Exchange servers, but leave a couple of servers behind for user management.

For detailed information about this, please refer to the following article about the common scenarios to to decommission your on-premises Exchange servers in a hybrid deployment:
https://technet.microsoft.com/en-us/library/Dn931280%28v=EXCHG.150%29.aspx?f=255&MSPPError=-2147217396

Regards,