Exchange Utility can only process up to 3 mailboxes in a single batch run. (4372130)

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Title

Exchange Utility can only process up to 3 mailboxes in a single batch run.
Description
The following errors were observed in the ExchangeUtility.wlog:
System.AggregateException: One or more errors occurred. ---> System.AggregateException: One or more errors occurred. ---> Microsoft.Identity.Client.MsalUiRequiredException: Your app has been throttled by AAD due to too many requests. To avoid this, cache your tokens see https://aka.ms/msal-net-throttling.
...
System.AggregateException: One or more errors occurred. ---> Microsoft.Identity.Client.MsalUiRequiredException: Your app has been throttled by AAD due to too many requests. To avoid this, cache your tokens see https://aka.ms/msal-net-throttling.
- Adding additional proxy credentials does not help.
- Attempted the message reconstruction in batches and still, only the first 3 mailboxes were processed.
Cause

Expected behaviour. Exchange Utility is currently only able to process 3 mailboxes in a single batch due to MAPI limitation when connecting to Exchange Online via modern authentication.
Resolution

Currently, there is no workaround to this MAPI limitation.

Customers migrating to Exchange Online are reminded that message reconstruction (back to their mailboxes hosted by on-premise Exchange server) are to be performed prior to the migration. This also avoids possible corruptions that might occur during migration that could cripple reconstruction attempts post-migration.
Additional Information

Despite the error, the product codes were reviewed and confirmed by Dev that Archive Manager is using the cached OAuth tokens for Autodiscover only. Exchange Utility is dependent on MAPI and modern authentication for Exchange connection, and the situation is a result of MAPI limitation.

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Exchange Utility can only process up to 3 mailboxes in a single batch run. (4372130)

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