> those that know this bog standard trick can still automatically derive your email address and get around your filters

Not if you default the other way around and autodelete all mail that doesn't have a "+thing". :V

Which causes major problems with those sites that refuse to accept an address containing a "+".

If you use Gmail then you have a couple of ways besides using the + to make a variation of your email address that will still come to your inbox:

1) Use dots (period or full stop) between letters in the username part of your email address. For example, if your email is [email protected] then [email protected] and [email protected] also get routed to you.

2) Use @googlemail.com instead of @gmail.com in your email address.

I have a Gmail address and I use these other variations whenever a company rejects email addresses with + in them.

Which companies are those? Is there a list somewhere? The only time I ever encountered this was with AliExpress.

Did that change? My AliExpress account is using [email protected]

I don’t know, I registered some time last year. Maybe it’s also the TLD? I have .me.

I've got a [email protected]. My dentist and several large companies refuse to accept this as a valid email address, so I have to use an email that doesn't identify me personally by name (uses efreak instead of my name). This annoys me every time I deal with them, especially since some of these sites use my email address as a username. I've been locked out from logging in on other devices a couple times for trying too many passwords when the problem was the address, not the password.

From memory, AliExpress wouldn't accept [email protected], but [email protected] was fine.

Interesting, so maybe I should have used a different prefix. Weird design.

I don't recall. I've only encountered it once or twice.