Yes, that is standard subaddressing but not all email providers support it (I've never heard of a Microsoft Exchange server supporting it). One problem with it is it exposes your real email address. Another problem, as the Wikipedia article notes, is there are a lot of inputs with poorly written validation that won't accept '+' as a valid email address character (they often only allow a-z, '.', and '@').

https://en.wikipedia.org/wiki/Email_address#Subaddressing

> I've never heard of a Microsoft Exchange server supporting it

It's supported on Exchange Online/Office 365 environments. There's a switch to enable it. We use it in our organisation.

This is a standard and every semi-smart spammer can strip the "\+.+" part so it works only with legit websites that you want to handle in a special way.

Fastmail has subdomain addressing [0] to solve that.

[email protected] is the same as [email protected]

[0]: https://www.fastmail.help/hc/en-us/articles/360060591053-Plu...

So, spammers will learn to look at the "domain.tld" at one moment if this gets popular.

another options is to buy a domain with a cpanel and set up a forwarder and filter to a specific folder in your secret main email account. The extra benefit here, since you own the domain, is that you can create a send identity of your [email protected]

Be careful with this. I once ordered something with Dell, and while their front-end system would accept my email address just fine, apparently one of their back-end systems choked on it, and not only did my order get stuck in limbo somewhere, but their customer service agents also couldn't easily fix it for me since their systems weren't able to handle this properly either.

I use this scheme. I have a separate account ([email protected]), were I only give addresses with aliases ([email protected]). There are of course broken sites, that do not allow + in the e-mail address. Also Bolt (bolt-rider.com) ignores the alias and just sends to the base address ([email protected]).

You can also add dots ('.') anywhere in a gmail address and still have it delivered. You can use an unary encoding of your random letters if necessary.