while I was on vacation for just a week a very dumb environmental monitoring system (by a major brand

So tomorrow, when I go back to work, I have to fix things. I got two question.
1) How can I filter senders that can from senders that musn't generate tickets? We use an A.D. LDAP backend for customers, so it would be great if we could limit the permitted senders only to LDAP users.
2) How can I safely and completely delete the thousands (around 2800) of tickets that the dumb monitoring system generated? I don't want to mark them as 'closed' or to have them lying around somewhere in the OTRS system, because they would completely distort statistics and so on.
Thanks in advance.
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rob