I have a question regarding setting up Azure AD Connect between On-Prem AD and an already existing Office 365 tenant.
Some time ago, a customer setup their mailboxes within Office 365. As mentioned above, it is completely independent of their On-Prem domain. There is no synchronisation between their On-Prem domain and Office 365 but there is now a need to install Azure AD Connect to start synchronisation. I found this MS article, https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnect-existing-tenant
, which helps but I have a few questions that I am hoping someone can answer for me.
1. If I test by filtering on a OU with a single account to ensure it works, will all other accounts in O365 get removed or will they be unaffected? I do not want to test if it going to cause greater problems.
2. I found that the On-Prem accounts still have a value for msExchMailboxGuid. I understand that under initial syncing, mailboxes may not be created. As the mailboxes already exist, would this value prevent O365 from mapping the O365 account to the correct On-Prem account? If it does, would clearing the value help?
Can anyone advise please?