For people who want to do this, be sure to get it right. I run a SaaS with a free tier, and I see people register with "fancy+nospam+servicename@gmail.com" addresses. Many of those become undeliverable or are left unread forever because of filtering rules. So when my system sends a warning E-mail that the account will be deleted due to inactivity, it doesn't get read, which leads to suboptimal outcomes for everyone involved.
Fucked up my Costco registration, a variety of other things.
This sort of quasi-pseudonymity is required for basic security/privacy in 2025; It's the only way to get a handle on who's allowed to send you email, since we've never bothered to fix spoofing or impose a cost on spam. I've been trying to use it since Sneakemail was a free service back in the pre-Gmail days.
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.
> Per-account alias might sound much
Not only does this not sound too much, this is a feature Apple offers called Hide My Email: https://support.apple.com/en-us/102548
With Apple's approach, I'd have to go through each account and move it from something@icloud to something@new-domain.
However, for people who don't want to mess around with custom domain names and e-mail providers, apple's approach is very practical. You just need to tell it to "hide your email" when you register somewhere and you're good to go.
It's super-easy to figure out who leaks my emails to whom, so I can easily disable both the leaker and the people who leaked.
Much more user-friendly than Apple's hide-my-email.
20-something-ish years ago I setup qmail in my VPS and a .qmail-default file captures all my me-sitename@vps emails. If they send me junk I echo '#' > .qmail-sitename and that's the end of it.
Other things that get a mixture like someone annoying who harvested my ebay/paypal addresses or something, I'll sift out the good (stuff I need) via maildrop and everything else gets junked.
Honestly one of the best, but annoying, things I've done, well worth the time invested as I have a nice clean mailbox.
I do too (anything@mysubdomain.example.com), but but online services collude with data brokers to share so much information [0] that I don't doubt that many of these "separate" profiles have been aggregated.
Unfortunately the services that supposedly offer to have your personal data removed from data brokers don't seem to support aliasing, so no straightforward way to either find out or have the data removed.
[0] Just look at the scary list of third-party cookies you can't opt out of on Coursera [1], for example:
Match and combine data from other data sources 419 partners can use this feature Always Active
Identify devices based on information transmitted automatically 546 partners can use this feature Always Active
Link different devices 358 partners can use this feature Always Active
Deliver and present advertising and content 582 partners can use this special purpose Always Active
I can opt out of all of them. The only third party cookie I can't is a cloudfront one for crsf.
The other good news in the meantime is that the EU (who originally mandated cookie consent) has finally woken up to the ridiculousness of leaving it up to the site, and will require browsers to enforce it instead.
Also started migrating old accounts in free time.
Now its pretty easy to tell the source of leak by email addresses as well as sources of spam.
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Per-account alias might sound much, but using sieve filtering [1] is amazing, and you can get a comprehensive filtering solution going with 'envelope to' (the actual address receiving the email) + 'header to' (the recipient address you see, sometimes filtering rules don't filter for BCC or sometimes recipients are alias instead of your actual email) that are more comprehensive than normal filtering rules to sort your emails into folders.
[1]: https://datatracker.ietf.org/doc/html/rfc5228
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Amusingly, I've managed to recover old accounts from emails that contains my old passwords with demands for crypto payment, it just provided me enough help to recall old variations of my passwords.