The phone support person was confused about that symbol too, what an odd email.
As some other comment suggested, these rules are easy to tackle by motivated spammers.
I've started using grouped aliases instead for a bunch of things.
Sure it is, but at least you do get later, post leak, a slight chance find out where leak originated.
Data stealers seldom strip out that +extension part before the selling or otherwise dump it somewhere. And while it's passed on, you get to see address as you gave to that party that had leak. Reason seller don't strip of it is perhaps because they sell by number of unique addresses and while +extension usage is quite rare they make more money when they don't strip it off too.
Information where it leaked can be very useful information to pass leaker at least up till point they have announced they know about the compromise happened. I've done that since turn of century too many times I've lost count already and been quite many times the first to get them know that they had a problem there.
And sure I've received thank you emails that I gave them early head-up info about the issue.
On some level, my employer uses emails as the primary key for customer accounts, the baseline identifier which all information is filed under. It's quite ridiculous.
I've lost track of the number of places that use the e-mail as an unchangeable identifier. Bonus points for my company liking to change domain names for sport, which just confuses support.
And even big tech companies, who should know better, do this. Like the big blue CDN that's in the middle of half the web's traffic. Who also, for some reason, can't be arsed to send e-mails reliably if you need to change your account.
Had to get an engineer involved.
This does help in filtering spam though
Since we're all using a unique password for every service - <cough> we are doing that, aren't we (!!) - then how does that help?
I would say they could fuck all the way off, but there are legitimate reasons to not let people sign up with an alias (like one person signing up for multiple free trials)
I have such a hard time understanding why people think e-mail addresses are some kind of special thing hard to come by.
That's why services like Firefox Relay exists. Just generates a new email address for you whose inbox gets relayed to your regular email, no fuss needed. I don't personally pay for it but I do use the heck out of the free email addresses they provided.