With gmail you can also simply add some text after a +
e.g.
cole.christensen+hnspam@gmail.com
And when mail from that source becomes troublesome setup a filter based on that To: address.
e.g.
cole.christensen+hnspam@gmail.com
And when mail from that source becomes troublesome setup a filter based on that To: address.
Maybe the problem you're running into is that the + character is special in URL's and must be escaped, otherwise it is treated as the representation of a space character. E.g. the URL parameter in <http://foo.example.com?unsubscribe&bob+whatever@domain> looks, after URL decoding by the server, like "bob whatever@domain". The software which inserted the e-mail into the URL didn't treat the plus properly, but the software which is decoding the URL is treating it like it is supposed to.
If that's the issue, the workaround could be as simple as manually fixing the URL in your browser, replacing the unescaped + character with its percent-encoding equivalent, %2B, as in <http://foo.example.com?unsubscribe&bob%2Bwhatever@domain>. The URL parameter bob%2Bwhatever@domain should now decode into bob+whatever@domain.
Try it next time.
It's easy to see how this could happen because the insertion of e-mail addresses into unsubscribe links in e-mail bodies is done by ad-hoc software probably cobbed together in house, whereas whereas URL parsing is done by generic URL handling code in a web server.
(But anyway, the whole point of this exercise is that we don't trust the unsubscribing. If unsubscribing could be trusted to be honored, we wouldn't need this extraneous e-mail address that we can recognize and junk.)
You could not, for instance, widely publicize your "plus armored" gmail address in ways that make it susceptible to harvesting, and the scheme won't safeguard against situations where that e-mail address, once given legitimately, ends up sold to spammers.
Basically, everyone should have their own mail domain with a different trick. :)
Here is something you can do to bootstrap your own trick: make a "plus armored" gmail address your main one. For instance "bob.smith+rocks@gmail.com", such that "bob.smith@gmail.com" is considered invalid and thrown to the bit bucket. Do not give the "+rocks" version to anyone other than close contacts. Since "rocks" is a personal suffix, a spammer who has the address "bob.smith+junk003@gmail.com" cannot guess that "junk003" must be replaced with "rocks".
My email address isn't Fort Knox. Email I don't want just doesn't get past the spam filters; even at peak spam a few years back when I was getting 4000+ illicit messages a month. Complex schemes aren't going to benefit me any because despite publicly posting my email as above, I just don't have a problem with unwanted messages.