Search-Mailbox – Powerful but Limited
Search-Mailbox is a very powerful cmdlet. It can search user mailboxes to find and remove content, or copy content to another mailbox, or both. The usual situation when Search-Mailbox is called into use is when someone, invariably an important person (in their minds, anyway), makes a mistake and sends email when they shouldn’t have and now wants every trace of the message eradicated. Search-Mailbox can do this, but only within the boundary of a single Office 365 tenant, and only in user and shared mailboxes.
Another common scenario is when some inappropriate or malicious content is circulating in email. If you can construct search criteria to find the bad content, Search-Mailbox can track it down and erase it, again from user and shared mailboxes.
No Group Mailboxes
Search-Mailbox can’t deal with group mailboxes, so it cannot erase content posted to the Inbox of Office 365 Groups nor can it remove Teams compliance records from the Team Chat folder. Removing compliance records might seem to be a bad thing, and normally it is, but if you do this to force Teams to synchronize the deletions back to its Azure data services and so remove the bad content from channel conversations, it could be a good thing. If, that is, appropriate authorizations are sought and granted to allow deletions to proceed.
The reason why Search-Mailbox is limited to user and shared mailboxes is that it was built many years ago to run inside an Exchange on-premises environment where the only objects it might have to process were user and shared mailboxes. Apart from making sure that it can understand queries expressed in KQL-syntax, Microsoft hasn’t done much to Search-Mailbox since Exchange 2010.
Dealing with Non-Mailbox Content
Search-Mailbox cannot process documents stored in SharePoint or OneDrive for Business libraries, or sways, plans, or forms, or any of the other non-Exchange content created by users and found inside Office 365.
If you need to run a search to find information across all the Office 365 workloads, you can use a content search, which covers Exchange (including public folders), SharePoint, OneDrive, and Teams. Once you’ve found the information, you can add a purge action to the search and have it remove items. But here’s the downside – content searches can only purge 10 items at a time and can only soft-delete information. In other words, the deletions can be reversed.
Probably with good reason, Microsoft has not yet allowed content searches to hard-delete items from the workloads it supports. Perhaps this is because the same kind of backups that exist on-premises don’t exist in the cloud, and if you made a mistake and permanently removed some information, Microsoft wouldn’t be able to retrieve that information. When backups don’t exist, soft-deletion and a nice period in a recycle bin seems like a good idea.
But Search-Mailbox does hard-delete items, which is what you want to do with malware or other objectionable material in mailboxes, so it’s a powerful tool that needs to be handled with care.
For more information about Search-Mailbox, see Chapter 6 of Office 365 for IT Pros. For more information about content searches, see Chapter 20.