During the deprovisioning process CloudManager can transfer the deprovisioned user's mail. The transfer is on a user-by-user basis and if deprovisioning large numbers of users it can take a very long time. The following can help improve the performance of the transfer.
1. Change the deprovisioning policies in CloudManager, so that the deprovisioned users will migrate mail to separate user accounts rather than transferring the mail into one account. The deprovisioning policy will need to be changed with every deprovisioned user, changing the email address to the specific destination user every time. See the screenshot below.
The advantage of this is that you can prioritise which user processes first as the deprovisioning options become available after each run.
2. Use CloudMigrator Pro to first migrate the mail over to the destination before you start deprovisioning, once the mail has been migrated you can start the deprovisioning without enabling the option for transferring the mails. This will significantly speed up your deprovisioning process as CloudMigrator Pro can handle multiple migrations at the same time.
Both of these workarounds will need you to cancel the currently running deprovisioning process.
If you need licenses for CloudMigrator Pro, please contact your account manager.