Compared to simplelogin (or proton pass aliases, addy, firefox relay, etc), one other downside of a catchall is in associations across accounts. Registering with a @passmail.net address implies that I use Proton; registering with random-string@mydomain.org implies I have access to that domain. If 10 data breach leaks have exactly one account matching the latter pattern then that’s a strong sign the domain isn’t shared. If one breached site has my mailing address, my real identity can be tied to all the others.
Compared to simplelogin (or proton pass aliases, addy, firefox relay, etc), one other downside of a catchall is in associations across accounts. Registering with a
@passmail.netaddress implies that I use Proton; registering withrandom-string@mydomain.orgimplies I have access to that domain. If 10 data breach leaks have exactly one account matching the latter pattern then that’s a strong sign the domain isn’t shared. If one breached site has my mailing address, my real identity can be tied to all the others.