Legacy on-prem journal mailboxes

Copper Contributor


We have legacy third party on-prem archiving solution that was archiving emails over many years.  Since moving to office 365 , we have left solution as is.. Now we want to decommission this server/solution and was planning on exporting the Journaling mailboxes to several PST files and then hopefully use a Powershell script to automate the importing into 365 shared mailboxes.


However Office 365 shared mailboxes have a limit of 50GB in size and one of our journaling mailboxes is 450GB in size!


Does anyone have any ideas how I can move these  huge Journaling mailboxes off on-prem servers to a cloud solution that users or just IT admin can access if they need to access old emailsl?





3 Replies

That scenario is against the usage terms/license agreement, as mentioned for example here:  https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/e...


Archive mailboxes can only be used to archive mail for a single user or entity (such as a shared mailbox) for which a license has been applied. Using archive mailboxes as a means of storing mail from multiple users or entities is prohibited. For example, an IT administrator can't create a shared mailbox and have users copy it (through the Cc or Bcc field, or through a transport rule) for the explicit purpose of archiving.

Technically, you can assign the necessary license and enable auto-expanding archive for the mailbox and ingest data up to the 1.5TB limit.

@Vasil Michev 


Hi. Thanks for your reply.


According to this article  , there is a restriction of 1GB of data growth per day - would importing the PST files attribute to this data growth limitation and would I technically be able to automate the import of multiple PST files without restrictions?


Also, you mentioned about relevant licensing...if I used a shared mailbox would licensing still apply and I assume that 1.5tb archive also applies to shared mailboxes?





@Vasil Michev please advise on the above. Thanks