That is a fair few emails to check, Have you tried setting a custom email rule under options? The default option would be to check for any unseen emails and if you are not marking them as read on each run I suspect it will be trying to process 30,000 emails on each run.
Unseen is the default value but you are in the right place, You would need to find an option that works for your mailbox. Maybe a filter on the date so something like [ 'UNSEEN', ['SINCE', 'Octover 31, 2022'] ]
Looking at the API docs it expects the path so it would depend on what the Mail Server calls it. That looks like it could be Inbox/Support unless the server gives it a different name.