The ideas site does not accept e-mail addresses which contain plus symbols in the local part.
Coming from an organisation headed by Rev "Pedant" "I like to do things right" K, this is pretty poor!
Worse than that, having wrongly assessed my valid e-mail address as invalid, it then throws me back to the data entry page, but all the text I spent the last 5 minutes writing has now disappeared!
Now you may have your own fine and fancy ideas about what constitutes a valid e-mail address.
But round where I live, we know no better than to consult RFC5322, which is only the normative standard which defines what constitutes a valid e-mail address.