Incoming Mail Queue configuration cannot be migrated from Server to Cloud. On Server, there is a special feature called purge strategy (for details, see: Incoming Mail Queue)but there is no corresponding feature on Cloud. Apart from this, the Incoming Mail Queue feature works the same way on Cloud as on Server.
The following figure shows the purge configuration options on Server:
Note that as of now, migrating existing queue entries from Server to Cloud is not possible. An automated migration tool will be available later this year for this purpose.