https://meta.wikimedia.org/wiki/Special:Contact/Stewards and other metawiki contact pages have been a couple of times the target of spamming bots. This would flood the OTRS queues that handle the emails generated by the contact pages and cause significantly more work for the volunteer OTRS agents.
While tracking down the IP and stopping a specific incident was possible up to now since the ContactPage  extension is configured to add that to the subject of the outgoing email, the attackers have switched patterns and are now sending those emails from multiple IPs ,effectively making this a game of whac a mole.
Spam filters are also not useful since those emails are generated from our own infrastructure which is inherently trusted (and we don't want to change that currently)
We have ConfirmEdit enabled so we can use that in the longer term to thwart those kinds of attacks