With Google Apps there is no limit to how many mailboxes can be extracted concurrently via OAuth, but Google Apps does have extraction throttling that they impose on the mailbox level. ODME will migrate as much data as the Google limit will allow however if we hit that limit than no other activities can be performed on this mailbox within a 24 hour period.
To work around this we have introduced a configurable limit to the amount that ODME will migrate in a given 24 hour period. 10GB is a recommended limit so that the migration does not interfere with other activities on the mailbox however this can be customized to the environment, or the limit can be increased and allow ODME to simply hit the limit for max throughput if you have no reason to access the mailbox via other means.
CAUTION: if ODME hits the limit than no other access will be granted to the mailbox which will affect other applications using the Google Apps API. Once ODME hits this limit ODME will pause the migration until a 24 hour period has passed since the start of this migration and then extract another 10GB and then pause the migration again until a 24 hour period has passed since the start of this second migration, etc.
For example let's say a user has a 20GB mailbox. The migrations is started at 3 PM. The first 10 GB is migrated by 11 PM (this is just an example and not the real speed) at this time ODME will pause and then start the next 10GB at 3 PM the next day.
ODME supplies an option to set a data extraction limit for Google migrations. ODME will pause migrations for 24 hours once the specified amount of data has been migrated.
The maximum ODME is permitted to extract is on the Options tab in the ODME plan as shown below: