john...doe@gmail.com doesn’t seem to work though. I don’t think Gmail takes multiple dots.
But sure, you could have `(my name is)john."..".doe+spam(...)@gmail.com` if you wanted to. Syntactically valid! The parenthesised bits would be stripped out before sending, and I have no idea whether Gmail would be willing to accept the quoted dots bit.
As for parens, I recollect the spec lets you nest your parens and quotes! It's insane. e.g. `f(oo."(bar."baz")."quux)@example.com` is valid in the spec.
I wrote an Oracle regex to parse for valid email addresses and I went against the spec rather than what is what's practically used. It was an insane thing.