I got a request recently. Due to audit purposes, they gave me like 100 keywords and delete those emails where ever they are in the server.
Exchange 2010/2013/2016 and Office365 is much powerful and easy to do such tasks. We can use the discovery search feature to accomplish it.
Click the below Link – Make sure the Admin has appropriate Permissions
https://www.azure365pro.com/deleting-a-specific-email-from-entire-organization-in-exchange-2010-2/
$search = '"expenses" OR "credit" OR "tax audit" OR "Payment"'
Saved the 100 Keywords to $search in the above format.
To move Content to a Specific Mailbox –
This example searches all mailboxes in your organization for messages that contain the words in $search . The search results are copied to the administrator Mailbox in the folder Exportedmailbox
Get-Mailbox "EntermailboxName" | Search-Mailbox -SearchQuery $search -TargetMailbox "administrator" -TargetFolder "ExportedMailbox" -LogLevel Full
To Delete Content
For Specific mailbox
Get-Mailbox "EntermailboxName" | Search-Mailbox -SearchQuery $search –DeleteContent
For All mailbox
Get-Mailbox | Search-Mailbox -SearchQuery $search –DeleteContent
To Estimate how much mails you are going to delete (Logonly Switch)
Get-Mailbox "EntermailboxName" | Search-Mailbox -SearchQuery $search -TargetMailbox "administrator" -TargetFolder "ExportedMailbox" –LogLevel Logonly
Add on –
Deleting a Subject from all mailboxes – But  Excluding a Specific Sender (Logonly Switch)
Get-mailbox -Resultsize Unlimited | search-mailbox -searchquery {Subject:"Welcome to dubai" NOT from:"administrator"} -Logonly -Targetmailbox administrator -Targetfolder Inbox
Clearing Dumpster of a Specific Mailbox – (Clearing DeletedItemsSize to 0)
search-mailbox MAILBOXNAME -SearchDumpsterOnly -DeleteContent
