How to delete mails from the Inbox of another user?

A VB (bad) app sended aprox. 13.000 mails to a user mailbox (a test message,
like Hello World)
Exchange shows 13.000 messages on the User Inbox (a 100 MB limit mailbox)

How to delete the messages

Option 1)
Recall. Recall wil not work, because the sender app, was not MS Outllook,
right?

Option 2)
Open user's Inbox with MS Outlook, using the credencial of the Exc 5.5
service account and delete all mails

Option 3)
type http://server/exchange/userloginname/inbox, supply exchange service
account credentials and delete all messages, in groups of 20 (OWA shows 20
each time)

Option 2 is now OK, MS Outllok hang, maby due to excessive number os
messages
Option 3 will, work? If so, can a i do a "select all"? Can OWA show more
than 20 messagens each time?