I do appreciate everyone's helpful advice to start using virtual email addresses.
I already do that with my active email address, which is shielded behind SneakEmail and SurfSolo and works through SeaMonkey Portable.
The problematic email address is the unencrypted 'standard issue' one my ISP provides, which I set up to work with Thunderbird, and which is just for a few contacts that don't really generate a lot of emails--until recent spam problems.
I've successfully defended that email address from spammers for the last 10 or 15 years, using KnujOn, among other things.
Then an important service needed an email contact for me over the telephone, and I gave my ISP email address out as a convenience since I wasn't near my computer, and next thing I know it's getting all this spam.
MailWasher is settling down somewhat now, but when it bounces spam, that prevents me reporting it to KnujOn, so I don't know if I'll stick with MailWasher, or quit that and just start reporting all the spammers to KnujOn.
Maybe I can figure out how to report it to KnujOn first, and then bounce it anyway using MailWasher.
KnujOn is NoJunk spelled backwards, and they have a delay factor between reporting spam and them shutting it down by tracking down the sources and reporting them to law enforcement authorities.
But with patience over the built-in delay in their response time, they've been surprisingly effective over the years.