When updating profiles, additional mailboxes are not updated in the profile. (49241)

When a profile is updated using CPUU, the additional third-party mailboxes that were in the original profile are not displayed in the updated profile once processed by CPUU unless these additional mailboxes have also been migrated.

If the third-party mailbox has never been migrated then the mailbox permissions will not have been added to the corresponding target mailbox & if the mailbox whose profile is being updated does not have permissions to the third-party mailbox then it will not be added to the profile.

When the third-party mailbox is finally migrated for the first time, as part of this process the target mailbox is always deleted & re-created, therefore the profile would not in any case contain a link to the same additional mailbox, so the problem will not resolve automatically by migrating the additional mailbox at a later date.

It is recommended to migrate groups of users who collaborate with each other together, then permissions are all set correctly in the target environment & this issue does not arise.