How to migrate mailbox with over 500 GB - Migration from GWS to M365

Brass Contributor


I am trying to migrate GWS mailboxes with over 500 GB to M365 utilizing third-party tool.

I have around 50 mailboxes over 200 GB and 10 mailboxes over 500 GB.

With third-party tool, I can migrate Gmail to archive mailbox of M365.

and I am aware of the fact that it needs auto-expanding feature of archive mailbox.

So I have enabled auto-expanding feature for those archive mailbox.


However, the thing is the daily growth rate and 

It cannot exceed 1GB/day as I noticed through below link.

The link says like this.

Auto-expanding archiving is supported only for mailboxes used by individual users or for shared mailboxes with a growth rate that doesn't exceed 1 GB per day.


Is there any way to speed up the growth rate?



And provisioning speed also matters. 

the link goes like under.

After you turn on auto-expanding archiving, an archive mailbox is converted to an auto-expanding archive when the archive mailbox (including the Recoverable Items folder) reaches 90 GB. It can take up to 30 days for the additional storage space to be provisioned.


Is there any way to shorten the days for the additional storage space to be provisioned?


How can I overcome this circumstances?

or is there an other method to do this?


Thank you in advance.

6 Replies
I think regarding your topic you should talk to Microsoft support directly, this forum can only assist you in guiding you towards correct direction. Anything outside official support documentation should be addressed directly to MS.
I feel that such large mailboxes should not exist in MS world and a process how to keep them in the standard size should be implemented, or the Exchange system is not the correct tool for use.

Hello, Thanks for your advice.

We have tried to contact MS SR once, and only got the link below. 


Have you ever experienced to contact Microsoft support directly for addressing migration for large mailbox?

To migrate GWS mailboxes (including 50 over 200 GB and 10 over 500 GB) to M365, use a third-party tool for Gmail migration. Ensure the auto-expanding feature is enabled for M365 archive mailboxes to accommodate the large data volumes during the migration process.


Thank you for your feedback.


We are using third-party tool for Gmail migration.

And auto-expanding feature is enabled as well.


The matter is expanding speed limited to 1GB/DAY.

For mailbox over 500GB, it seems to need 400 more days to complete the migration...


Is there any idea for handling mailbox over 500 GB?


Thank you.

In my experience Microsoft support won't be able to do much to speed this up. You might be able to speed it up a little's some insights that might help:
Thank you for sharing your knowledge.