Mass delete inbox in RingCX/Engage Digital

This customer has email submission forms that were spammed thousands of times with fake outreach by the same user. While filters/rules can be deployed post-facto (in addition to a ReCAPTCHA), clearing up only the SPAM emails is currently a limitation, and the customer wants a way to either:
-purge threads based on specific criteria from the email, allowing them to target the spammer
-enable mass selection of messages in the inbox view (a 'select all' checkbox, and/or a filtering feature to narrow messages in the inbox to just the SPAM messages, which can then all be selected for deletion)