Hello, @Ashutosh Kumar,
Welcome to the Microsoft Q&A platform!
Based on your description, I understand that you have a comprehensive plan for migrating from Forest A to Forest B and would like some advice on how to ensure a smooth migration.
Migrating Active Directory (AD) and ensuring uninterrupted mail flow can be a complex process, here are some tips to help you make a smooth transition.
About how to ensure continuous mail flow while migrating objects to the new forest, the following steps are recommended:
1.Properly configure the Hybrid Configuration Wizard (HCW) in both forests, which will help maintain mail flow during migration.
2.Ensure that the mail flow between Exchange Online and the local Exchange server is configured correctly by sending and receiving test emails.
If you want to configuring Azure AD Connect in the new environment without causing synchronization issues, here are some things to keep in mind:
1.When setting up Azure AD Connect in a new forest, use mS-DS-ConsistencyGuid as the source anchor point, which will help maintain consistency and avoid synchronization issues.
2.Use Azure AD Connect in staging mode in the new forest, which allows you to verify configuration and synchronization without affecting the production environment. Once all objects are migrated to the new forest, disable AD synchronization in the source environment to prevent any conflicts.
As for additional considerations and practices to follow during this migration process, please refer to the following points:
1.Before the formal migration, set up a test environment to simulate the migration process, identify possible problems, and verify the effectiveness of the solution.
2.Ensure that you have up-to-date backups of all data prior to migration and have an emergency recovery plan in place to prevent data loss due to unexpected issues.
3.Implement a mail flow monitoring tool during the migration process to monitor the transmission of emails in real time and identify and resolve transmission failures in a timely manner.
4.Regularly review Exchange and Azure AD Connect logs to identify potential errors or warnings that can provide important troubleshooting information.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Thank you for your support and understanding.
Best Wishes,
Alex Zhang