Hi,
We had an accessibility audit and one of the issues was that the error message for email fields was not helpful enough and should contain something about the format it expects. Personally I disagree and think the message is good enough, but perhaps it is worth to look into.
I decided to create a patch instead of overriding the email class because the latter would not keep track of any possible future changes to the Email field.
Sincerely,
Dagomar