"Opt in" email servers

I run the medicinal herblist.

And today, I got a question from a (currently) former list member, asking why she was unsubscribed.

I sent her an email explaining that mailman automatically unsubscribes everybody who bounces ...

... and my explanation bounced right back to me with this:

"Undelivered Mail Returned to Sender"
"[the former listmember's email address]: host mx4.[bouncing ISP][the boucing ISP's current mailserver IP number] said: 554 Failure SPF NEUTRAL, (grey) to fix send an email to allow-mkey-[my current IP number]@mx4.[bouncing ISP] then resend original email, see http://[unrelated URL] (in reply to end of DATA command)"

Which means that either she or all of her ISP have switched to "opt in" email: everybody who doesn't jump through their fancy new hoops is bounced.

Needless to say, I'm not going to jump through any hoops, nevermind how shiny and new, just to explain to her that she's been unsubscribed because she or her ISP bounce back all mail from everybody who doesn't jump through said hoops. (Neither will anybody else with at least two braincells).

So. If you (or your ISP) change your email settings to "opt in", whitelist or similar, please ensure that your mailing lists are opted-in, whitelisted or similar from the start.
Because if you don't, you'll wonder where your mailing lists went. Along with pretty much all your former email friends, who likely don't even know how to read bounce reports ... and thus have no idea why they can't reach you over your old email address anymore.

--

Why do I think that this is a mindblowingly stupid way to deal with spam? Let's just ponder what happens if it catches on, and two such setups hit each other. Will either ever receive email from the other? Ponder ponder ponder. Got there? Well done!

As to the question "how do I get back onto the list", well, turn that silly thing off, then resubscribe. And, and this is important, don't turn it back on. Your online social life will thank you.