Downcase email on signup

Sometimes people signup with a capital letter for an account, while their actual emailadress is all downcased. Leading to not finding the list they are admin of in the webinterface.

While email would be case-sensitive (afair) most email providers actually treat emailadresses as case-insensitive. So I would suggest to downcase the email on signup. Actually we should do the same on schleuder side, not?

I would suggest to downcase subscriptions in schleuder and hence also the email field of an account with the possibility of breaking email providers that are case-sensitive. But honestly, I think they will be in way more sever problems than schleuder not respecting their casing.