Replying to
@bocops@fosstodon.org Does your email host support sieve scripting? If so, you can already do this with ManageSieve.
If not, you would need to do it the way you’re describing - have a mail client connected 24/7 filtering for you.
I would personally grab a raspberry pi, install a desktop environment and then grab Thunderbird. Run thunderbird 24/7 and have it do the filtering for you (yes, thunderbird can filter emails)