TIL that email-addresses can have comments.
> `john.smith(comment)@example.com` and `(comment)[email protected]` are both equivalent to `[email protected]`
Here, hold my beer, I'm off, breaking that regex validation in your app.
@doenietzomoeilijk I deliberately did not reverse my statement 'if it arrives, it's valid' does not mean 'if it doesn't arrive it's invalid'.
But give email some slack: it can handle downtime perfect. It can handle improper implementations. 'Arrived' may imply 'it can be read', but that's secondary.
And no: if a person can read the email, the address was valid. Fully. No 'reasonably sure' there, but 100% sure.
(Again: that does not mean if a person cannot read it, its invalid.)