This is a neat idea, and I'd really like to see it implemented in HIBP.
Having said that, I also question how far should HIBP go and adjust for the quirks of individual email providers. Generic sub-addressing is a standard (rfc5233) and implemented by nearly every provider, but going all the way would be much more involved than that.
A few examples of such quirks:
1) AFAIK, dot addressing is something specific to gmail. Other email providers (like Hotmail) treat JaneDoe@outlook.com and Jane.Doe@outlook.com differently.
3) For domain equivalence, gmail.com and googlemail.com are equivalent, but contrary to what one of the comment below claims, JaneDoe@outlook.com and JaneDoe@hotmail.com are different accounts.
Generic plus addressing is a good idea, but I feel implementing support for every possible email address equivalence might not be as useful for the effort involved, especially when the other problems are much more easily solvable by registering just one more account in HIBP.
Anjor
This is a neat idea, and I'd really like to see it implemented in HIBP.
Having said that, I also question how far should HIBP go and adjust for the quirks of individual email providers. Generic sub-addressing is a standard (rfc5233) and implemented by nearly every provider, but going all the way would be much more involved than that.
A few examples of such quirks:
1) AFAIK, dot addressing is something specific to gmail. Other email providers (like Hotmail) treat JaneDoe@outlook.com and Jane.Doe@outlook.com differently.
2) For plus addressing, Yahoo allows users to create a separate prefix for disposable addresses e.g. JaneDoe@yahoo.com will have addresses of type "CustomPrefix-foo@yahoo.com" and "CustomPrefix-bar@yahoo.com" (Also note the - instead of +)
3) For domain equivalence, gmail.com and googlemail.com are equivalent, but contrary to what one of the comment below claims, JaneDoe@outlook.com and JaneDoe@hotmail.com are different accounts.
Generic plus addressing is a good idea, but I feel implementing support for every possible email address equivalence might not be as useful for the effort involved, especially when the other problems are much more easily solvable by registering just one more account in HIBP.