I recently enable online archiving for a user who's mailbox was in excess of 30GB to help with performance as she was constantly updating and having connection issues due to the amount of mail she was accessing through searches and what not.
I got a report yesterday that her archive was missing items. Upon investigating I was able to determine she was missing almost 2 whole years of emails within the archive. I got this information using Powershell Commands on Exchange.
Search-Mailbox mailboxname -SearchQuery {Received: "10/2/15..07/31/17"} -TargetMailbox Mailboxname -TargetFolder foldername
ResultItemsCount : 87
ResultItemsSize : 36.84 MB
When I checked her Online Archive size it was only 21GB and her Mailbox has only 4GB in it so I can see that there is roughly 8GB of emails missing and the results show that there are almost no emails between those dates.
Is there a known issue regarding this or any way to see if these items are recoverable? It has been roughly a month since the archive was created. I am also unsure if the online archive uses any sort of compression resulting in it being smaller than the
data that was moved from the mailbox.