Thomas.Poett@TEAMS (MVP Teams and Cross-Tenant M&A/D Migration Expert Lead)

How to hide and un-hide users from Global Address List (GAL) in Exchange Online if they are AD Connect synchronized Hiding User from GAL isn't possible if those are synchronized form On-Premises Active Directory. The local AD is the leading system for all important attributes, like SMTP, UPN and hiding from GAL. Especially during a cross-tenant migration, you do not want to see not migrated user in the GAL. Those User aren't actively working until their cut-over day. Since the Exchange Online attribute  msExchHideFromAddressList s is an AD on-premises parameter, we have two possible ways hiding user in BME from GAL.   Modify the AD Connect for your teant with a custom rule, by using a extensionAttribute to set the HidefromGAL. In this rule, for users which have an entry in the extensionAttribute, hiding / un-hiding will be controlled by AD Connect This is the best option for Cross-Tenant Migration, if you run 2 or more AD Connect system We direct modif...

  Example of our user data migration approach: Important is the completion of your data pre-load for OneDrive and Exchange. Remember, that the pre-load should include as much data as possible. Syncing on the cut-over day data > 10 GB or more than 500 files in OneDrive, might end up with an INCOMPLETE set of data in the target. Therefore, you should urge using the OneDrive Cross-tenant OneDrive Migration tool from Microsoft. The user will than see data being migrated (missing data) upon he starts working in the target environment. This will not be happening with the cross-tenant migration tool. The switch to the target tenant will take approx. 15min. Migration of Teams personal Chat messages, we mostly limit to 15 days. The performance is acceptable migrating approx. 400 – 800 users/day. Note: You should have special procedures in place for legal-hold users, white glove and user object facing issues. Prepare source and target tenant and ensure the readiness for Microsoft...

  Personal Data migration Exchange and OneDrive In the previous chapters, it is stated: Teams make use of several M365 service. Especially for the personal side of Teams, Exchange and OneDrive are heavily involved. Towards Teams migration, it is required, that ALL data is present in the target environment for Exchange Calendar and OneDrive (shared files).   Data Pre-Load Data pre-load is much slow than you expected. This is the most important lesson learned. While Exchange is faster than OneDrive, be aware of the time required for the data copying process. Another important statement is: none of the existing solutions are SYNC solutions, data is only copied. Therefore, a co-existence and working parallel in both, source and target tenant can lead to data inconsistence. If data is changed in the target environment and in source, any delta sync will overwrite the target data, if source has a new change date. Same, if the target data is newer, changed source data wi...