Considerations when disabling or enabling AD Accounts during migration (4351541)

Target accounts have been created as disabled user accounts with Linked Mailboxes.  Is it okay to enable those accounts when migration is finished?  Is it okay to disable source accounts?  Are there any disadvantages or known issues when doing this?

In some situations admins decide to enable the target account manually and then they change a few attributes so the mailbox is displayed as regular user mailbox and not as linked mailbox.

Things to know (a simple, non-technical explanation):
When starting with migration QMM (DSA) creates the target account as disabled user account.
Since a mailbox cannot exists without an owner DSA will set the source account to be the Associated External Account and this account will have all rights to this mailbox.
Target disabled user will only have SELF rights.
Later you decide to enable the target user manually. But according to Microsoft only a disabled account can have an AEA (MsExchMasterAccountSid populated), and now your enabled account still has this attribute populated, this is problem one
Problem two: you enabled the target user account but target user still has the same permissions he had in past, only SELF and not full mailbox rights or owner. This might cause undesired issues later.

Proper way is to re-migrate those users using a migration session and during this migration session to disable the source account and enable the target account, then DSA will set permissions correctly and change the target linked mailbox to be a regular one.

Here is an article which explains: https://support.quest.com/migration-manager-for-ad/kb/35991

There is one serious issue when doing this in the middle of migration. The Exchange server in source will notice that the source account got disabled and then it will act accordingly and remove some Exchange permissions, this can happen with Public Folders and with mail data.

Here is an article which explains: https://support.quest.com/exchange-migration-wizard/kb/45135
This should be taken into consideration when deciding whether to disable source accounts or not and when this should be done exactly, at which stage of migration.Quest support cannot advise which procedure should be used, to clarify this please contact the Account Manager and ask for assistance, Quest Professional Services can assist with migration planning.

This article is to provide some information which might be helpful when answering questions or when deciding about the migration strategy.