This allows me to sign up at any webpage with a different email address, to make filtering easier and to quickly learn if someone is selling my email address if I use a unique email address per signup. My webhost has done this to allow people a basic for of catch all address that isn’t really a catch all.
In theory this sounds great, but in 2 days I have some across 2 websites that don’t support this at all. Dell.com was the first one I found. The Dell site told me they wouldn’t accept the email address. Fine, I created something else to use.
thehip.com did something far worse. They accepted the email address, then mangled it when they put it in a database, and somehow replaced the + with a space. This has very bad consequences when the site sent me an email. So “email@example.com” got turned into “fred firstname.lastname@example.org”. When the site sent the email, all of a sudden email@example.com and firstname.lastname@example.org received the email (that contained my password by the way). This kind of failure is very bad (IMO).
I hope more sites will support plus style addressing. I plan on using it a lot more.