How do you delete specific message from users in Exchange 2013 DAG database?

Question

Our network has been inundated with spam from INTUIT.COM with the SUBJECT: PAYMENT OVERDUE and contains a link to download a form from a Dropbox. Obviously, very suspicious and clearly spam. We're using Postini as our Edge Transport/ Spam filter but messages
are still getting in. I've enable anti-spam on all my mailbox servers, set the SCL values but that hasn't worked.
I understand that Exchange Edge Transport role has the more aggressive spam fighting features but Microsoft also recommends an online spam filter. 
Needless to say, we've taken steps to quarantine those messages based on subject and sender in Postini but now would like to delete those messages from the users in went to. My users are two different DAG mailbox databases. I found this article http://www.techieshelp.com/delete-mail-from-multiple-mailboxes/ but
the command didn't work. I'm thinking its because I have DAG and a couple of databases. I even tried "get-mailbox -database "databasename" | search-mailbox -searchquery subject: "Payment Overdue"" and that didn't work. 
I'm running Exchange 2013 SP1 DAG across two sites comprised of four 2013 SP1 mailbox servers.

Answer 1

Check this out
http://technet.microsoft.com/en-us/library/ff459253%28v=exchg.150%29.aspx and specifically look at the section titled  "Search messages and log the search results"
Or you can use this
http://technet.microsoft.com/en-us/library/aa996371%28v=exchg.150%29.aspx with the WHATIF parameter
Alternatively if you are open the 3rd party solutions check out Lucid8's DigiScope
http://www.lucid8.com/product/digiscope.asp
which would allow you to see the search results and then delete OR if desired you can set the On FIND action to Export to PST and then Delete so that you can preserve and then remove messages on the fly as the search system finds
Search, Recover, & Extract Mailboxes, Folders, & Email Items from Offline Exchange Mailbox and Public Folder EDB's and Live Exchange Servers or Import/Migrate direct from Offline EDB to Any Production Exchange Server, even cross version i.e. 2003 -->
2007 --> 2010 --> 2013 with Lucid8's
DigiScope