@jean-marie,
The issue of uppercase letters in user email addresses causing email sending problems in wpForo profiles is likely due to CSS or display formatting rather than the actual email address stored. However, if the problem is that emails are not sent because of uppercase letters, email addresses should be treated as case-insensitive by the mail system. To fix display issues where text appears in uppercase, you can override CSS rules that force uppercase text by adding custom CSS to your forum settings. For example, add a CSS rule to reset the text-transform property to normal. This can be done in Dashboard > Forums > Settings > Styles Tab > Custom CSS code area. Unfortunately, there is no direct mention of email sending issues caused by uppercase letters in user emails in the provided context. If the problem persists, please check your email sending configuration or contact your hosting provider for server-related email issues.